REVIEW: The role of ecosystems and their management in regulating climate, and soil, water and air quality

Authors


Correspondence author. E-mail: pete.smith@abdn.ac.uk

Summary

  1. Ecosystems have a critical role in regulating climate, and soil, water and air quality, but management to change an ecosystem process in support of one regulating ecosystem service can either provide co-benefits to other services or can result in trade-offs.
  2. We examine the role of ecosystems in delivering these regulating ecosystem services, using the UK as our case study region. We identify some of the main co-benefits and trade-offs of ecosystem management within, and across, the regulating services of climate regulation, and soil, water and air quality regulation, and where relevant, we also describe interactions with other ecosystem services. Our analysis clearly identifies the many important linkages between these different ecosystem services.
  3. However, soil, water and air quality regulation are often governed by different legislation or are under the jurisdiction of different regulators, which can make optimal management difficult to identify and to implement. Policies and legislation addressing air, water and soil are sometimes disconnected, with no integrated overview of how these policies interact. This can lead to conflicting messages regarding the use and management of soil, water and air. Similarly, climate change legislation is separate from that aiming to protect and enhance soil, water and air quality, leading to further potential for policy conflict.
  4. All regulating services, even if they are synergistic, may trade off against other ecosystem services. At a policy level, this may well be the biggest conflict. The fact that even individual regulating services comprise multiple and contrasting indicators (e.g. the various components of water quality such as nutrient levels, acidity, pathogens and sediments), adds to the complexity of the challenge.
  5. Synthesis and applications. We conclude that although there are some good examples of integrated ecosystem management, some aspects of ecosystem management could be better coordinated to deliver multiple ecosystem services, and that an ecosystem services framework to assess co-benefits and trade-offs would help regulators, policy-makers and ecosystem managers to deliver more coherent ecosystem management strategies. In this way, an ecosystem services framework may improve the regulation of climate, and soil, water and air quality, even in the absence of economic valuation of the individual services.

Introduction

In this study, we focus on how climate, soil, water and air quality are regulated by ecosystem processes in a way that provides some benefits to human well-being. Collectively, these benefits are increasingly referred to as ecosystem services. Whereas it is typically the environmental variables that are assessed or monitored, the development of appropriate policies and management practices would benefit from an improved understanding of how changes in ecosystem processes affect the delivery of ecosystem services. The Millennium Ecosystem Assessment (2005) placed ecosystem services into four main groups: (i) provisioning, for example, food, fibre, water; (ii) regulating, for example, climate, water quality; (iii) supporting, for example, soil formation, nutrient cycling; and (iv) cultural, for example, aesthetic and recreation benefits. The regulating ecosystem services we examine in this study were described in Smith et al. (2011), but the interactions between these services, the policy drivers and conflicts, and co-benefits and trade-offs are examined in detail for the first time here. Understanding the interactions between services is important if we are to appreciate the implications of developing policy and payment mechanisms around the promotion of particular ecosystem services into economic markets. Discussion around the potential of payment for ecosystem services is increasing (Farley & Costanza 2010), as well as discussion about more integrative management institutions (Barnes et al. 2008).

Analysis of cross-linkages between different ecosystem services is complicated because they may be composed of many different physical and chemical components, which are subject to multiple (or different) environmental drivers. For example, while some air pollutants, such as ozone (O3), consistently reduce primary production, others, such as sulphur and nitrogen, can increase primary production in some terrestrial ecosystems at moderate deposition rates, but reduce primary production in other ecosystems at higher deposition rates. So, ecosystems are sometimes affected by the same broad drivers in quite different ways.

This study describes the ecosystem services we focus on (section ‘'Description of the ecosystem services: climate regulation, and soil, water and air quality regulation'’), outlines the interactions between these and other ecosystem services (section ‘'Interactions between climate, and soil, water and air quality regulation and other ecosystem services'’), examines how the drivers affecting these ecosystem services have changed over the past 20 years (section ‘'Drivers of change in the regulation of climate and soil, water and air quality by ecosystems'’), and how the services themselves have changed over the same period (section ‘'Recent trends in the regulation of climate and soil, water and air quality by ecosystems'’). It then examines the policies that have affected these ecosystem services (section ‘'Synergies and trade-offs between actions to regulate climate and soil, water and air quality'’) and the synergies and trade-offs arising from actions to regulate climate, and soil, water and air quality (section ‘'Policies affecting the regulation of climate and soil, water and air quality by ecosystems'’). We conclude by outlining future needs (section ‘'Future needs'’). We intend this review to act as a reference point for future work on these regulating services, so we have tried to deal in specifics as much as possible, and have provided referenced examples wherever possible. We recognise, however, that it is impossible to represent every aspect of these complex processes within a single overview and therefore anticipate that this review will provide a step towards the more comprehensive and integrated assessment of regulating ecosystem services in the future.

Description of the ecosystem services: climate regulation, and soil, water and air quality regulation

Climate regulation

Ecosystems regulate global and regional climate (i) by providing sources or sinks of glasshouse gases (affecting global warming) and sources of aerosols (affecting temperature and cloud formation); (ii) by enhancing evapotranspiration and thereby cloud formation and rainfall (Kleidon, Fraedrich & Heimann 2000); and (iii) by affecting surface albedo and thereby radiative forcing and temperature (Betts 2000). Ecosystems can also affect the microclimate locally, through the provision of shade and shelter and the regulation of humidity and temperature. This regulation of microclimate can have a noticeable impact on human well-being, particularly in the urban environment. The components of the services and how ecosystems regulate these components are summarised in Table 1.

Table 1. Components of each ecosystem service contributing to the overall ecosystem service (climate, or soil, water or air quality regulation) – and how these are regulated by ecosystems
Ecosystem serviceEcosystem processHow this process is regulated by ecosystems
Climate regulationCarbon (C) storageC is stored in vegetation and soils including peatlands. Growing vegetation and well-managed soils can remove C from the atmosphere (Lal 2003; Smith 2012a), and ecosystem management can regulate CO2 emissions to the atmosphere. The fate of any harvested C is also important (e.g. timber used in housing may store carbon for hundreds of years). Colluvial and alluvial sediments also store C (Noe & Hupp 2005; Quine & Van Oost 2007; Van Oost et al. 2007)
Transfer of heat and moistureEvapotranspiration from vegetation and soils controls the amount of water vapour entering the atmosphere, regulating cloud formation and radiation transfer in the atmosphere (Kleidon, Fraedrich & Heimann 2000)
Nitrous oxide (N2O) and methane (CH4) emissionsManagement of ecosystems (drainage/rewetting of wetlands, livestock and fertiliser management) can influence N2O and CH4 emissions (Le Mer & Roger 2001; Dobbie, McTaggart & Smith 1999) e.g. ammonia (NH3) emissions from livestock and fertiliser use can lead to increased fluxes of glass house gases (N2O and CH4) after deposition to terrestrial ecosystems (Sutton et al. 2011)
Aerosol formationVegetation and soil erosion produce aerosols that can reflect or trap solar radiation (cooling or warming) and affect cloud formation (Kanakidou, Seinfeld & Pandis 2005)
Change in albedoDarker surfaces reflect less of the sun's energy and trap warmth in the atmosphere. Planting more trees can reduce albedo, especially where there is often snow cover (Betts 2000)
Microclimate regulationProvision of shelter from heat, Ultraviolet light, wind and precipitation. Local regulation of temperature, humidity and precipitation.
Soil quality regulationBuffering, filtering, degradation and retention of pollutants and nutrientsInfluenced by the type, amount, timing and duration of pollutant/nutrient inputs set against local characteristics of soil (e.g. texture, pH, biology, etc.). Management and vegetation cover influence contaminant inputs and remediation. (Alloway 1995; Kalbitz et al. 2000)
Soil organic matter creation, storage and respirationDependent on balance between biomass formation by vegetation (dependent on temperature, water, solar radiation), and respiration (increased by high temperature, cultivation and reduced water content)
Retention of soil sand, silt and clay particles against erosion by wind and waterInfluenced by land use and management under local climatic conditions and vulnerability of soil types (Boardman & Evans 2006; De Vries et al. 2009; Van Oost, Cerdan & Quine 2009)
Water capture, retention and movement mitigating flooding and soil droughtinessRainfall is captured and stored by soils. Movement to groundwater and other water bodies regulated by the landscape of soils, influenced by land use, vegetation types and management practices such as drainage and irrigation. (Holman 2006; Rounsevell, Evans & Bullock 1999)
Suppression of pests and diseasesSoil microbial community composition/activities and soil chemical elements can affect diseases and pests. Management can influence soil suppression (Janvier et al. 2007; Weller et al. 2002)
Regulating gas exchange with the atmosphereUptake and release of gases by soils influenced by soil moisture and temperature, activity of soil microbes and availability of plant substrates. Land use and management of ecosystems can influence gas exchange
Water quality regulationNitrate retentionPlant uptake, soil accumulation, denitrification (e.g. in riparian zones). Ecosystem regulation depends on form and timing of nitrogen (N) input in fertilisers, organic matter amendments or atmospheric deposition, as well as agricultural practices, soil and vegetation type, and infiltration/drainage
Phosphorus retentionPlant uptake, soil accumulation, infiltration rates and water flow pathways (phosphorus release is associated with sediment transport in overland flow)
Organic pollutant and pathogen regulationAssimilation, adsorption and mineralisation of organic matter by the ecosystem. Increased by water infiltration and storage, for example, via riparian buffer strips and shelter belts below farmland
Sediment and particulate organic carbon (POC) retentionSediment losses are low from managed landscapes with high water infiltration rates and storage, but increase with exposure of bare soil, surface compaction and drainage. POC losses are low from intact peatlands, but can increase in several orders of magnitude following loss of vegetation cover and erosion (Evans et al. 2006). Reconnection of river channels to their floodplains increases removal of suspended sediments and associated nutrients into medium to long-term storage (Noe & Hupp 2005; Nicholas et al. 2006)
Buffering of acidityWell-buffered soils neutralise acidity via weathering and cation exchange. Low-nutrient soils retain atmospheric N, and waterlogged soils such as peats retain sulphate via reduction processes. Land management practices can affect the ability of upland soils to retain or buffer atmospheric contaminants
Dissolved organic carbon (DOC) regulationOrganic soils such as peats naturally leach coloured, high-DOC water. This reduces the depth of aquatic plant growth, increases water treatment costs and associated health risks, and may increase mobilisation of some toxic substances, but also provides a source of energy for aquatic ecosystems, and protects aquatic organisms against UV radiation. DOC leaching is reduced from acidified soils (Monteith et al. 2005) but may be increased by management-related disturbance, particularly in peatlands (Rowson et al. 2010)
DilutionClean water from headwater catchments can dilute contaminant inputs from downstream point or diffuse sources to safe levels. Most important during low-flow periods and therefore dependent on catchment water storage
Prevention of algal bloomsAlgal growth in streams and lakes can also be reduced by riparian shading (e.g. Hutchins et al. 2010). This may help to reduce the impacts of algal blooms (in the case of blue-green algae, toxic) in eutrophied freshwaters, where terrestrial and aquatic nutrient retention are insufficient to counter diffuse and point sources of nutrient pollution
Water temperatureWater temperature can affect survival and reproduction of aquatic organisms. Temperature extremes can be reduced by shading via riparian tree planting
Air quality regulationDeposition of air pollutantsDeposition of pollutants to vegetation and soil from the atmosphere can significantly reduce air concentrations (Fowler et al. 2009), and hence, reduce adverse effects on human health and other ecosystem services. However, the deposited pollutants may adversely affect vegetation, and soil and water quality (RoTAP 2012)
Emissions of air pollutantsManaged ecosystems in particular release pollutants to the atmosphere that may subsequently be deposited elsewhere, with polluting effects on sensitive ecosystems. For example, NH3 and NO2 emissions from livestock and fertiliser use, which are influenced by ecosystem management, may lead to increased deposition of N, or direct toxicity, to sensitive plant species (Sutton et al. 2011)
Emissions of pollutant precursorsSoil and vegetation emit compounds that contribute to formation of secondary pollutants in the atmosphere. For example, volatile organic carbon emissions from vegetation contribute to ozone and aerosol formation (Royal Society 2008)

The UK has large amounts of carbon (C) ‘locked up’ in its forests, peatlands and soils (114 Mt C in vegetation; approximately 9840 ± 2460 Mt C in soils; Milne & Brown 1997; Bradley et al. 2005; Dawson & Smith 2007). Anthropogenic activities (e.g. forest management, agriculture, management burning) govern large fluxes of glasshouse gases to and from the atmosphere, and any sustained net flux to the atmosphere will ‘draw down’ on the long-term carbon capital. Projected ‘business as usual’ emissions from the UK land use, land-use change and forestry (LULUCF) sector in the next fifteen years show this sector switching from being a net sink of carbon dioxide (CO2) to a net source (Thomson & Hallsworth 2011). The UK has both national (UK Climate Change Act) and international commitments to reduce net glasshouse gas emissions. The projected costs of dealing with climate change are considerable and will increase if mitigation actions are delayed: the Stern review (Stern 2007) estimated that not taking action would cost 5–20% of global gross domestic product (GDP) each year, whereas reducing emissions to avoid the worst impacts could cost 1% of global GDP each year. While the current focus is on reductions in the use of fossil fuels, the agriculture and LULUCF sectors will play an increasing role (DECC 2011).

Soil quality regulation

The ecosystem processes that regulate soil quality determine a host of other services (e.g. climate regulation, nutrient cycling, biomass production, water quality, pollination). The processes involve the interplay of physical, chemical and biological flows and properties that reflect a soil's capacity to buffer, filter and transform chemical substances. The components of the service and how ecosystems regulate these components are summarised in Table 1. Many aspects of soil quality in all UK broad habitats have been degraded by human actions over the last 50 years, for example, by atmospheric pollution and poor management practices. The role of ecosystems in regulating soil quality is reflected across spatial scales from local scale feedbacks between plant and soils (e.g. in regulating C and nutrient dynamics) through to landscape interactions between land uses and soils (e.g. influencing the movement and transformation of waters and pathogens). The consequences of soil degradation are a general reduction in their capacity to store, regulate, buffer, filter and transform chemical substances. Current trends indicate that recovery from, and remediation of, both diffuse and point source contamination is in progress (Smith et al. 2011).

Water quality regulation

Water quality encompasses many different parameters, including nutrient levels, acid-base chemistry, organic pollutants, pathogens, pesticides, industrial and pharmaceutical products, suspended sediments, colour and temperature. As such, it is difficult to generalise about either the overall direction of change in water quality, or the role of ecosystems in regulating it. However, in broad terms, it is those aspects of water quality that are most strongly associated with catchment sources or processes where the potential for ecosystem regulation is greatest. This is particularly evident in upland areas, where major water quality issues are associated with the deposition of atmospheric pollutants such as sulphur, nitrogen and metals, as well as high levels of water colour associated with dissolved organic carbon (DOC) production by organic soils, which increases water treatment costs and may lead to health issues associated with disinfection by products generated during the treatment process. In general, upland water quality has improved in the UK since the 1980s, as lower atmospheric pollution levels mean that terrestrial ecosystems are better able to buffer lakes and streams against acidification and nitrate leaching. However, these improvements have been offset by increases in DOC and water colour, which have been attributed to recovery from acidification (Monteith et al. 2005). Upland management practices, notably peat drainage, rotational moorland burning and over-grazing, have the potential to degrade ecosystem water quality regulation by enhancing DOC production, reducing soil retention of contaminants, and increasing suspended sediment loss from exposed soil surfaces.

In agricultural landscapes, water quality issues include run-off of nutrients, pesticides, organic pollutants and pathogens from livestock, and suspended sediments from disturbed soils. Terrestrial ecosystems play a key role in regulating diffuse contaminant transport to surface waters, particularly via the infiltration and retention of pollutants into soils. Soil compaction due to over-grazing can reduce infiltration rates and therefore increase contaminant transport into water bodies, as can disturbances such as forest felling or ploughing. However, these problems can be partly mitigated by catchment-sensitive land management such as the use of riparian buffer strips, continuous cover forestry and improved farm nutrient management. These regulating services are, however, vulnerable to climate change, particularly the increased incidence of extreme high flows.

Other water quality issues are associated with point sources, ranging from industrial discharges and waste-water treatment plants to smaller point sources such as septic tanks in rural areas. Improved regulatory control of larger point sources (rather than changes in ecosystem water quality regulation) has been a major driver of improved water quality in the UK over the last 30 years. However, upstream ecosystems can play a key regulatory role in the dilution of point source pollutants entering downstream river systems, mitigating their impacts on aquatic ecosystems and water supplies. This regulating service is again sensitive to both land management and climate change, with land-use practices that retain water within the landscape helping to sustain flows during drought periods, and climate change likely to increase drought severity. Finally, the management of water bodies and adjacent land can help to mitigate water quality; for example, riparian shading can help to reduce water temperatures and algal blooms, while improved connectivity between rivers and their floodplains can enhance sediment, nutrient, organic pollutant and pathogen removal. The components of this service and how ecosystems regulate these components are summarised in Table 1.

Air quality regulation

The exchange of trace gases and particles between ecosystems and the atmosphere means that ecosystems can be a source of air pollutants, or their precursors, but can also have positive effects on air quality, primarily through interception, deposition and removal of pollutants (Fowler et al. 2009). However, if the rate of this deposition exceeds critical thresholds, there may be adverse effects on a range of other ecosystem services. Emissions to the atmosphere from ecosystems can also directly and indirectly degrade air quality. The components of the service and how ecosystems regulate these components are summarised in Table 1.

In terms of air quality itself, rather than ecosystem regulation, there have been significant improvements in the UK over recent decades, primarily due to reduced anthropogenic emissions from the transport, energy and industry sectors. In contrast, the main drivers of changes in the ecosystem service of air quality regulation over recent decades are likely to have been those changes in land use and management, which influence deposition and emission of pollutants. Despite the significant improvements in air quality, current concentrations and deposition rates still exceed thresholds for effects on human health, crop and forest production and biodiversity over large areas of the country (Defra 2007a, 2010; RoTAP 2012).

Quantification of the health effects of air pollution in the UK has suggested an annual value between £8 and £20 billion (Defra 2007a, 2010). These effects of particulate and gaseous air pollution are of considerable societal concern; for example, the external costs of transport in English urban areas due to poor air quality are comparable to those of accidents, delays and physical inactivity (EAC 2010). Increases in local particle deposition due to urban tree planting (McDonald et al. 2007; Tiwary et al. 2009) and decreases in national-scale O3 deposition in drought summers (Emberson et al. 2012) have been shown, respectively, to decrease and increase the impacts of air pollution on human health, indicating the significance of ecosystem air quality regulation. However, the overall net value of the air quality regulation provided by UK ecosystems in terms of human health has not been estimated.

The direct effects of air pollution in degrading ecosystem services in the UK have also not been quantified, although some initial estimates are available; for example, Mills et al. (2011) estimated that O3 caused an annual loss of yield for arable crops in the UK of £180 million. For some specific policy interventions, the benefits of air quality management policies in terms of ecosystem services could be comparable in size to those for human health. For example, Smart et al. (2011) estimated that the value of scenarios to reduce UK ammonia (NH3) emissions were comparable in magnitude in economic terms for effects on human health, ecosystem carbon sequestration and ecosystem nitrous oxide (N2O) emissions. However, no study has yet quantified the effect of air quality on a full range of ecosystem services, and significant barriers to such an endeavour exist in terms of both data and models. A fuller discussion of these issues, and a wider range of possible values for the benefits of air quality policy to ecosystem services, is provided by Jones et al. (2011).

Agriculture, which accounts for about 66% of UK land use, represents a significant economic cost in terms of its net effect on climate change, air and water quality (Spencer et al. 2008; Table 2). Graves et al. (2011) have also calculated the total annual cost of soil degradation in England and Wales to between £0·9 and 1·4 billion, with a central estimate of £1·2 billion. The greatest costs were associated with the loss in organic matter (45%) and compaction (39%).

Table 2. Summary of environmental accounts for UK agriculture, 2007 (Spencer et al. 2008)
Annual flows£ million
Benefits
Landscape616
Biodiversity1088
Waste services37
Total1741
Costs
Climate change1371
Air quality634
Flooding244
Fresh water144
Drinking water160
Soil erosion11
Waste7
Total2571
Total benefits less cost −830

Interactions between climate, and soil, water and air quality regulation and other ecosystem services

There are interactions between these regulating services, and with other nonregulating ecosystem services. The key interactions are shown schematically in Fig. 1, which provides an illustration of the effects of a range of land management practices cascading through different regulating services. Some examples of such interactions are summarised in Table 3.

Table 3. Links between climate, and soil, water and air quality regulation and other ecosystem services
Ecosystem serviceEcosystem processEffect on other regulating servicesEffect on supporting servicesEffect on cultural servicesEffect on provisioning servicesEffect on biodiversity
Climate regulationC storage; NO2 and CH4; aerosol formation

Mineral soils with high C levels can generally store more water and nutrients, and show greater resistance to erosion (Annabi et al. 2007).

Increased forest planting increases deposition rates of pollutants from the atmosphere

Primary production: affects C stores and regulates glass house gas (GHG) emissions and removals from the atmosphere

Soil formation: maintenance of this is vital to the stability and growth of long-term C stores in peatland

Areas with significant C stores (forests, moorland) are frequently used for recreation, leisure and tourism

Lowland soils with high soil C, can generally maintain high levels of crop production.

Agricultural products: changes in cropland area and livestock management affect GHG emissions and removals

Forest products: Increased production of softwood (conifers) responsible for an increased forest C sink

Peat: extraction reduces and degrades long-term C stores

Biodiversity in all groups (especially micro-organisms, phytoplankton and land plants) has a key role in regulating GHG emissions, removal and C storage and moisture transfer

Bryophytes: key group for ongoing C sequestration in peatlands

Effect of vegetation on albedo, heat and moisture transfer, and turbulenceIncreased evapotranspiration due to vegetation can modify rainfall and thereby air, water, and soil qualityPotential primary production and the water cycle in an area is determined by the rainfall and temperature regimeClimate patterns have a significant effect on the culture of a societyIncreased rainfall, particularly in continental locations, can increase agricultural and forestry productionBiodiversity in a particular area is determined in part by water availability
Microclimate regulation by vegetationProvision of shade and shelter can increase water infiltration and retention (Marshall et al. 2009), reducing soil erosion and affecting water qualityChanged rainfall and temperature regimes can influence nutrient cyclingShade and shelter have roles in recreational activities (e.g. parks, gardens, streets)Shelterbelts can improve crop and animal productivity/welfareVariations in microclimate can increase niche types and thereby biodiversity
Soil quality regulationSoil organic matter creation, storage and loss; regulating gas exchange with the atmosphereC sequestration can help to mitigate climate changeSoils are important sinks and sources in global cycling of atmospheric gasesAreas with high organic matter can create distinctive landscapes (e.g. peat moorlands, Machair coastal grasslands, wetlands)

High soil organic matter can help maintain agricultural and silvicultural yields (Pan, Smith & Pan 2009; Kosmas et al. 2001; Quine & Zhang 2002)

Peat: extraction reduces and degrades long-term C stores

Peatlands of good ecological status support a wider range of biodiversity than degraded peats
Buffering, filtering, degradation and retention of pollutants and nutrientsSoil absorption of pollutants and nutrients can protect water qualityHealthy soils maintain soil formation and nutrient cycling (Bardgett et al. 2011)Reduced acidification and nutrient levels can help deliver ‘good ecological status’ in riversReduced leaching of nitrate and other nutrients can help maintain crop yields, and minimise fertiliser costsHealthy soils help to protect water biodiversity from pollution, pests and diseases
Retention of soil sand, silt and clay particles against erosion by wind and waterComplete vegetation cover can reduce soil erosion and protect water qualityMaintenance of soil depth is vital to support primary productionHealthy soils sustain species and habitats with conservation status (Erber, Bruneau & Black 2010)Maintenance of soil depth critical to maintain crop yields (Bakker, Govers & Rounsevell 2004)Good soil quality helps farmland birds, for example, food source
Water capture, retention and movement mitigating flooding and soil droughtinessRetention of water can affect water quality through dilution effects; high infiltration can minimise peaks in river flow.Soil water retention is important to maintain primary productionAnaerobic/poorly drained soils can help maintain culturally important archaeological remainsSoils with adequate aeration and water can maintain significant crop growth and yields (Kosmas et al. 2001; Quine & Zhang 2002; Heckrath et al. 2005)Healthy soils provide the appropriate soil gas concentrations for soil biological activity
Water quality regulationBuffering, filtering, degradation and retention of pollutants and nutrientsPoor water quality, for example, saline irrigation water, can lead to reduced soil qualityPoor chemical or microbiological water quality can render the water effectively unavailable for some services, for example, clean drinking waterLow levels of N and P in water can minimise eutrophication; improved appearance of lakes and streams; low level of organic pollutants and pathogens improves bathing water qualityHigh-quality water important for irrigated crops. Provision of high-quality drinking water. Reduced use of fertilisers and pesticides can significantly reduce crop yields. Rewetting and cessation of rotational burning for water quality may reduce upland productivity for agriculture or forestry

Good water quality supports aquatic biodiversity.

Ecosystem buffering of acid deposition protects recreationally important fish stocks

Air quality regulationSulphur (S) depositionS deposition can suppress methane emissions (Gauci et al. 2004)Soil acidification from sulphur and nitrogen deposition reduces microbial activity and nutrient cycling, and increases leaching of base cationsSulphur emissions contribute to aerosol formation, which can affect visibility; acid deposition causes corrosion of cultural heritage; acidification of water bodies related to recreational fishing; loss of biodiversity related to loss of educational value; ecotourism

S deposition can increase production in sulphur-deficient crops (RoTAP 2012)

Reduced acid deposition associated with recovering fish populations (Monteith et al. 2005)

Reduced acid deposition associated with recovering aquatic biodiversity (RoTAP 2012)
Nitrogen (N) depositionModerate N deposition increases tree growth and hence C sequestration (De Vries et al. 2009). N deposition increases N2O emissions

At moderate levels, N deposition can increase primary production.

Eutrophication can lead to imbalance in N:P ratios and induced P deficiency

N emissions contribute to aerosol formation which can affect visibility; acid deposition causes corrosion of cultural heritage; acidification and eutrophication of water bodies related to declines in recreational fishing and swimming; loss of biodiversity related to loss of educational value; ecotourismModerate N deposition increases above-ground biomass in N-limited ecosystems (Dise et al. 2011)N deposition decreases plant species diversity and soil biodiversity (Dise et al. 2011; RoTAP 2012)
Ozone (O3) deposition

O3 reduces C sequestration in vegetation (Sitch et al. 2007) and soils (Loya et al. 2003)

O3 modifies CH4 emissions (Toet et al. 2011)

O3 reduces primary production. Elevated O3 interferes with stomatal control of water loss (Mills et al. 2009) and can reduce catchment stream flows (Mclauhglin et al. 2007)Reduced visibility on smoggy days. Corrosion effects on cultural heritage; loss of biodiversity related to loss of educational value; ecotourismHigh O3 concentrations reduce crop yields and forest production (Mills et al. 2011; RoTAP 2012)Elevated O3 concentrations can change plant species composition (Wedlich et al. 2012)
Figure 1.

Influence diagram showing key interactions between six management interventions (bold typeface and shaded blue), which affect regulating ecosystem processes related to climate change and air, water and soil quality (italic typeface and unshaded), and four final ecosystem services (nonitalic typeface and shaded yellow). Dashed red lines indicate a direct negative relationship and solid lines indicate a direct positive relationship. The presence of dashed and solid lines indicate that there are trade-offs.

While some of the interactions lead to synergies (i.e. what is good for one ecosystem service is also good for another), there are also some trade-offs. These synergies and trade-offs are explored in more detail in later.

Drivers of change in the regulation of climate and soil, water and air quality by ecosystems

Table 4 summarises some of the main drivers of change occurring in the UK during the last 20 years. Although trends in drivers of change are given for the last two decades, it should be noted that changes in the drivers will not necessarily equate to changes in services over this time scale because some services have slow response times. Some services are still responding to drivers that happened over 20 years ago (e.g. legacy effects of land-use change), and some degraded services may take time to respond and to achieve full function after restoration. Indeed, the current status of many of our current ecosystem services is a reflection of drivers of change from hundreds, if not thousands, of years of agricultural land use.

Table 4. Drivers of change for regulation of climate, and soil, water and air quality by ecosystems over the last 20 years
Ecosystem serviceEffect of economic changeEffect of population/demographic changeEffect of land use and land management changeEffect of climate change
Climate regulationEconomic growth generally associated with increased energy use (predominantly from fossil fuels). Changing glass house gas emissions with reduction of UK manufacturing sector and switch from coal to gas power stationsIncreased urbanisation and artificial sealed surfaces; increased demand for energy, food and fibreExpansion of forestry, increased urbanisation and changes in agricultural managementChanging patterns of precipitation, increasing temperatures, increasing CO2, ocean acidification
Soil quality regulationIndustrial emissions and fossil fuel use as causes of pollution; increased trading has tended to lead to land-use specialisation: e.g. less mixed farmingDemands for, and changes in preferences of, food and fibre; urbanisation reducing the extent of prime agricultural soilsUse of inorganic fertilisers and slurries; reduction in crop rotations (especially ley grass – where fields are uncultivated in some years); changes in land drainage and cultivation practice; changes in woodland cover; remediation of contaminated landNo consistent climate change trends to date; higher temperatures are generally associated with increased soil C oxidation rates
Water quality regulationInternational trade has led to less heavy industry in UK: national reductions in SO2 and NO2 emissions, with less acidification of soils and waterIncreased water demand in South-East England leading to reduced capacity for pollutant dilution. Decreasing industrial demandReduced fertiliser usage, use of riparian buffer strips and shelter belts, peatland restoration, some reductions in upland land-use intensityIncreased low flow incidence/severity reducing dilution of pollutants within river systems
Air quality regulationAir quality is directly affected by increased energy and transport use, and by reduced industrial activityIncreased population, urbanisation and altered land-use patterns directly affect air qualityExpansion of forestry and changes in agricultural management modify ecosystem/atmosphere exchange of pollutants

Hot dry summers are associated with reduced deposition and higher air concentrations of pollutants.

Increased CO2 concentrations reduce stomatal uptake of pollutants

Recent trends in the regulation of climate and soil, water and air quality by ecosystems

Although many changes in services have clearly been determined by changes in drivers (Table 5), as indicated in Section ‘'Drivers of change in the regulation of climate and soil, water and air quality by ecosystems'’, there is not always a one-to-one correspondence between changes in drivers and changes in the ecosystem services (e.g. due to lag effects). Table 5 summarises the basic national trends in each ecosystem service, but these may disguise some important regional and seasonal shifts. For example, trends of reduced sulphur and nitrogen deposition over recent decades are less marked in the north and west of the country (RoTAP 2012). There are some examples where one ecosystem service has been impacted by another in opposite directions. For example, acid deposition has decreased over the past two decades, reflecting improved air quality. However, while this has reduced the acidity of water courses (generally a positive effect), it has also led to an increase in DOC leaching from soils to water courses (a negative effect).

Table 5. Recent trends in the ecosystem regulation of climate, and soil, water and air quality over the last 20 years
Ecosystem serviceProcessHow has this changed over the last 20 years?
Climate regulationC storageUK ecosystems have produced an increasing net sink of CO2 since 1990 (LULUCF sector in Brown et al. 2012), driven by forest planting over past 50 years. Soil carbon storage capacity has been lost in other ecosystems, particularly enclosed farmland although some soil carbon may have been stored below surface horizons (Quine & Van Oost 2007; Van Oost et al. 2007). Peatlands have not been fully accounted for in the LULUCF inventory to date
Albedo, heat and moisture transfer and momentumIncreased evidence of heat island effects in urban areas; can be mitigated by integrating urban green space including vegetated roofs
Nitrous oxide (NO2) and methane emissions (CH4)Nitrous oxide and methane emissions have fallen due to lower N fertilizer use in agriculture and reduced livestock numbers (Brown et al. 2012)
Microclimate regulationLoss of shelter from degradation of hedgerows and shelterbelts. Reduction in microclimate regulation potential in urban areas due to loss of greenspace
Soil quality regulationBuffering, filtering, degradation and retention of pollutants and nutrientsReductions in soil acidity attributed to reductions in acid rain (S deposition), while continued nutrient enrichment (eutrophication) attributed to N deposition and agricultural sources of N (RoTAP 2012). Improved guidance on uses of organic amendments, N and P fertiliser use helping to improve soil N status and water quality (Defra 2009)
Soil organic matter creation, storage and lossMuch research has focused on only the top 15 cm of soil, whereas a full assessment requires an assessment of changes in soil depth and changes in soil C content within the soil profile. Increased use of minimal tillage should help maintain soil C in arable areas. Removing drainage schemes can increase soil C
Retention of soil depth against soil redistribution by tillageSoil redistribution by tillage accelerated over the last half of the last century and has resulted in high spatial variability in cultivated soils on sloping land (Quine & Zhang 2002; De Vries et al. 2009; Van Oost, Cerdan & Quine 2009). Economic cost has not been quanitified but is likely subsumed in on-site costs attributed to water erosion
Retention of soil sand, silt and clay particles against erosion by wind and waterSoil erosion due to agriculture is estimated to cost the UK economy ca. £45M per year and £50–60M in off-site sedimentation costs (Defra 2009). Erosion risks from both wind and water have been exacerbated by intensification of land use; McHugh, Harrod & Morgan (2002); Grieve, Davidson & Gordon (1995)
Water capture, retention and movement mitigating flooding and soil droughtinessLimited data. Local studies demonstrate increased soil water retention with improvements in soil organic matter content and soil structure. Models predict greater susceptibility of light textured soils to drought (Brown et al. 2012)
Suppression of pests and diseasesLimited data. Expansion of New Zealand flatworm and Phytophthora spp. highlight increased risk to soil health and from movement of soils
Regulating gas exchanges with the atmosphereAs above, reduced soil emissions of glass house gases (GHGs) through improved fertiliser use. Historical losses in soil organic matter are now a potential C sink, with many managed soils well below C retention capacity. Degraded peats will remain sources of GHGs without extensive restoration (Joosten et al. 2012)
Water quality regulationNitrate retentionLittle evidence of improvement despite 32% reductions in fertiliser N applications (Defra 2009) and some reductions in atmospheric N deposition, suggesting degradation of ecosystem N retention function
Phosphorous retentionReduced concentrations in most rivers, but mainly due to regulation of point sources, and 53% decline in fertiliser applications (Defra 2009) rather than ecosystem regulating functions
Organic pollutant and pathogen regulationReduced biological oxygen demand in most rivers, and increased compliance with bathing water standards, again associated mainly with controls on point source (e.g. sewage) inputs, but also with better retention of organic pollutants via improved agricultural land management
Sediment and particulate organic carbon (POC) retentionLimited data, although improved agricultural and riparian land management, as well as restoration and revegetation of eroded upland areas, is thought to have reduced sediment loads
Buffering of acidityWidespread recovery from acidification in upland waters as ecosystems better able to buffer lower sulphur (and to a lesser extent nitrogen) deposition inputs
Dissolved organic carbon (DOC) regulationWidespread increases in upland waters associated with recovery from acidification, as organic matter solubility increases in less acid soils. Some evidence that these increases have been exacerbated by over-intensive upland management, particularly peat drainage and burning
DilutionData limited but could be possible to determine from hydrological records and trends in low flow occurrence/severity from NRFA
Air quality regulationSulphur (S) deposition to land surfaces

UK dry S deposition has fallen by 93% and wet S deposition by 57% from 1986 to 2008 (RoTAP 2012)

Deposition velocity of SO2 to bog surfaces halved from 1995 to 2006 (Fowler et al. 2009)

Nitrogen (N) deposition to land surfaces

Total UK reduced N deposition changed little from 1986 to 2008 despite decreased emissions (RoTAP 2012)

Total UK oxidised N deposition fell by 24% from 1986 to 2008 (RoTAP 2012)

O3 deposition to land surfacesRecent trends in total deposition are not quantified. Peak concentrations declined, but background concentrations increased over last two decades (RoTAP 2012)
Ammonia (NH3) emissionsNH3 emissions from agriculture declined by 27% since 1990, mainly due to reduced livestock numbers (Misselbrook et al. 2010)
Biogenic BVOC emissionsTrends in biogenic volatile organic carbon emissions are uncertain (RoTAP 2012)

Synergies and trade-offs between actions to regulate climate and soil, water and air quality

Improvements to one ecosystem service can often improve other ecosystem services (Table 6). For example, attempts to manage nutrient applications to farmland to avoid eutrophication and thereby improve water quality, are also effective at reducing glasshouse gas emissions, and thereby improve climate regulation. There are other examples centred around: the co-benefits from carbon sequestration that improve soil quality and create carbon sinks to improve climate regulation; better management of agro-ecosystems to improve water and soil quality; and woodland planting to reduce air pollution, create carbon sinks and benefit other nonregulating ecosystem services (Table 6). On the other hand, there are a number of potential trade-offs (Table 7). For example, soils can be used as a buffer to prevent contaminants from reaching water bodies, creating a clear trade-off between soil and water quality in these buffer strips. Similarly, buffer strips can lead to greater glasshouse gas emissions (e.g. through increased denitrification to stop nitrates reaching water courses, leading to increased nitrous oxide emissions), or to the eutrophication of semi-natural terrestrial systems (i.e. semi-natural habitats that trap the nutrients themselves suffer eutrophication when preventing the nutrients entering the water course). A number of other examples are presented in Table 7.

Table 6. Synergies between actions to regulate climate, and soil, water and air quality
Ecosystem Service receiving synergistic benefitsActions to affect the Ecosystem Service
Climate regulationSoil quality regulationWater quality regulationAir quality regulation
Climate regulationTree planting in urban areas to increase C sequestration can also reduce heat island effects (Wilby & Perry 2006)Increased soil organic C to improve soil quality can also act as a sink for atmospheric C, thus improving climate regulation (Smith 2012b)Improved nutrient management practices to minimise leaching, volatilisation and eutrophication will also minimise glass house gas emissionsReduced N deposition decreases N2O emissions
Soil quality regulationIncreased soil C to improve climate regulation can also improve soil qualityIncreases in soil C of mineral soils offers benefits in terms of water and nutrient retention, and buffering capacityMeasures to prevent transport of sediments (and associated pollutants) can maintain soil depthReductions in atmospheric NO2 and SO2 and associated deposition on soil can minimise soil acidification
Water quality regulationImproved management of organic soils to enhance C sequestration can reduce DOC and POC losses to freshwaters; Increased woodland planting generally associated with improved water qualityBetter farm nutrient management to protect soil fertility can reduce freshwater eutrophicationReduced sediment loads can reduce associated pollutants and thereby improve water qualityReductions in atmospheric NO2 and SO2 and associated deposition on soil can minimise water acidification
Air quality regulationTree planting in urban areas to increase C sequestration can reduce particle concentrations with benefits for human health (McDonald et al. 2007; Tiwary et al. 2009)Precision management of soil nutrients can reduce ammonia and nitric oxide emissionsMeasures to reduce nutrient run-off can reduce likelihood of coastal algal blooms, and reduce the associated atmospheric emissionsTree planting to capture particulates can also reduce urban concentrations of other pollutant gases
Table 7. Trade-offs between actions to regulate climate, and soil, water and air quality
Ecosystem Service receiving trade-offsActions to affect the Ecosystem Service
Climate regulationSoil quality regulationWater quality regulationAir quality regulation
Climate regulationActions to increase soil C stocks by creating anaerobic conditions (e.g. by rewetting of peatlands) may increase methane and N2O emissionsSoil drainage to remove anaerobic conditions and cultivation to remove soil compaction can reduce soil C storage

Nitrate removal in wetland buffer strips may increase N2O and methane emissions

Reductions in fertiliser use, while improving water quality, may reduce growth in N-limited ecosystems

Reduced N deposition may reduce growth rates and C storage in N-limited ecosystems

Reduced S deposition may increase methane emissions from soils

Soil quality regulationMaintaining anaerobic conditions to increase soil C storage can increase risk of acidification and leaching

Soil drainage and cultivation can increase aeration and reduce compaction, but can lead to decreased soil C and increased erosion risk.

Minimisation of soil tillage may increase soil compaction and increase potential for N2O emission (Ball, Scott & Parker 1999)

Soils can be used as a buffer to prevent pollutants from entering water courses, enhancing water quality but reducing soil quality in buffer zonesReduced N and S deposition could result in soils where lack of N and S limits soil processes and vegetation growth
Water quality regulationIncreased woodland planting can lead to reduced water flows (less dilution) and greater acidificationSoil drainage may improve soil aeration, but reduced duration of water retention may increase transfer of pesticides to riversMeasures to increase infiltration (less run-off) can be associated with increased risk of leaching and groundwater contaminationReduced S deposition has increased DOC in water courses (Evans et al. 2006)
Air quality regulationWoodland planting can increase pollutant deposition and is associated with greater acidification of sensitive soils and waters, and slower recovery with falling deposition (RoTAP 2012)Fertilisers and legumes used to improve soil nitrogen status can increase emissions of ammonia and nitrous oxideBuffer strips may lead to locally elevated NH3 and NO2 emissionsTree planting in urban areas to capture particulates and other pollutants can increase biogenic emissions that contribute to O3 formation; an effect that varies between species (Owen et al. 2003)

There are some good examples of integrated ecosystem management; however, some aspects of ecosystem management could be better coordinated to deliver multiple ecosystem services. The lack of an ecosystem services framework to assess co-benefits and trade-offs limits the ability of regulators, policy-makers and ecosystem managers to deliver more coherent ecosystem management strategies. Such a framework may improve the regulation of climate, and soil, water and air quality, even in the absence of economic valuation of the individual services.

While Tables 6 and 7 aim only to present examples of synergies and trade-offs between different regulating ecosystem services, it is clear that managing ecosystems to maximise the delivery of one ecosystem service may limit the capacity of the ecosystem to deliver other ecosystem services. On the other hand, some ecosystem management strategies benefit multiple ecosystem services. In the following section, we examine how current policy (using the UK and its constituent countries as an example) influences multiple ecosystem services.

Policies affecting the regulation of climate and soil, water and air quality by ecosystems

Synergies and trade-offs between ecosystem services, explored in the previous section, show that there are a number of potential policy ‘win–win’ options, but that badly formulated policy could lead to trade-offs between ecosystem services. A number of policies have been introduced in recent years to combat climate change or to protect or improve soil, water and air quality. In this section, we briefly review the relevant UK policies and legislation, describe the intended outcome and explore how policies introduced to impact one ecosystem service or environmental variable, have impacted upon other ecosystem services, focussing, as above, on regulating services.

We primarily focus on examples of where the impact of a policy on an environmental variable is mediated via an impact on ecosystems, that is, through the regulating service, as opposed to directly changing a driver (e.g. by banning a pollutant).

In the last few years, the UK and its devolved administrations (DAs) have introduced world-leading legislation to combat climate change. The UK Climate Change Act 2008 aims to cut glass house gas (GHG) emissions by 34% (rising to 42% with international agreements) by 2020 and 80% by 2050 compared with a 1990 baseline. Parallel legislation in Scotland under the Climate Change (Scotland) Act 2009 has equivalent targets of 42% and 80% by 2020 and 2050, respectively. Examples of policies aimed at using ecosystems to mediate this climate regulation in Scotland are the Farming for a Better Climate initiative intended to reduce GHG emissions from agricultural ecosystems (Scottish Government 2012) and the Scottish Forestry Strategy intended to increase vegetation carbon sinks through increase in woodland cover to 25% (Scottish Executive 2006). The Welsh Government has a target of 15% woodland cover, mostly through broadleaf planting. In the UK, the UK Biomass Strategy (Defra 2007b) aimed at increasing the area of perennial energy crops, and the use of organic waste and currently unharvested wood for energy, is a policy aimed at reducing GHG emissions through ecosystem management. However, there could be trade-offs, for example, through increased particle levels in the air from widespread use of wood stoves.

A number of biodiversity and habitat protection policies also enhance ecosystem services. For example, the Lowland Raised Bog Habitat Action Plan, which aimed for 90% of the total market for soil improver and growing media to be peat-free by 2010, has resulted in a reduction of peat extraction and rehabilitation of degraded bog habitat, but has also enhanced the carbon sink provided by these areas, delivering improvements to climate regulation, soil and water quality. The England Biodiversity Strategy (Defra 2011a), which seeks to halt the overall loss of England's biodiversity by 2020, emphasises the role of agri-environment payments. Recent agri-environment payments to landowners, such as the differing levels of environmental stewardship, have tended to emphasise biodiversity and soil and water quality enhancement, rather than regulation of the climate and air quality. However, the next round of rural development programmes (2014–2020) places a much greater emphasis on climate regulation. The Scottish Biodiversity Strategy (2005) provides a 25-year vision for action to protect Scotland's biodiversity. Delivery of the strategy includes a focus on maintaining healthy and productive ecosystems, developing actions to sustain and support the complex web of conditions and organisms that contribute to productive soils. Although soil itself is often not directly protected under such designations, management agreements and operations often provide enhanced soil protection to enhance the biodiversity, geodiversity and landform value of sites. However, there are several Species Action Plans that are directed at soil species, for example, tooth fungus and wood ant, which deliver biodiversity protection through improved soil management. In Wales, the Glastir agri-environment scheme will target funding towards areas with greatest potential for enhancement of soil carbon storage, and water quality and quantity regulation, as well as biodiversity and cultural services such as landscape, access and the historic environment.

While direct soil protection legislation such as the European Union (EU) Soil Thematic Framework (2006) and the Scottish Soil Framework (2009) have influenced soil quality directly, policies directed at other environmental variables have also benefited soils, or been implemented through improvements in soil management. Flood management legislation, for example, such as the EU Floods Directive and the Flood Risk Management (Scotland) Bill use catchment focussed approaches to integrated flood management, and rely on appropriate soil management as a central plank in their implementation. Similarly, under the EU Water Framework Directive (2001/60/EEC; and Nitrate Vulnerable Zones legislation), the environmental protection of water resources not only directly improves water quality, but also leads to improvements in soil quality.

Agricultural policies also affect a number of ecosystem services, with the Common Agriculture Policy (including the use of Good Agricultural and Environmental Condition), including a number of soil protection measures, which will enhance soil organic matter content, soil structure and reduce the risk of erosion, thereby delivering a benefit through enhancing regulating ecosystem service provision. Other rural development policies, such as the Rural Development Programme for 2007–2013 (e.g. the Prevention of Environmental Pollution from Agricultural Activity Code in Scotland), have positive implications for air, soil and water quality. Specific measures for soils include testing soil, nutrient planning, creating wetlands, converting arable land to grassland and leaving uncultivated buffer strips alongside watercourses to minimise diffuse pollution of water and to retain eroded soil in the field. Land managers are able to minimise pollution and gain benefit to their businesses through good soil management. In the forestry sector, the Revised Forests and Soils Guidelines under the UK Forestry Standard (Forestry Commission 2011) identify the importance of forest soils and outline good practice requirements to protect and enhance forest soils through sustainable forest management practices considering its interactions with water, biodiversity and air quality.

National Planning Policies and Environmental Assessment legislation also have components that improve the delivery of ecosystem services. National planning policies offer protection to soils through policies aimed at preventing inappropriate development in a wide range of areas and are major means of delivering sustainable urban drainage systems and soil remediation, thereby helping to enhance soil and water quality. The Environmental Assessment (Scotland) Act 2005 and UK Strategic Environmental Assessment legislation both ensure greater consideration of the environment in the preparation of plans, programmes and strategies, thereby gaining the opportunity to minimise unforeseen environmental impacts. Soils are explicitly considered alongside air and water. Scottish Natural Heritage also has planning guidance, which aims to protect ecosystem services.

Legislation also helps to facilitate the remediation of historically contaminated soils (e.g. Contaminated Land Regime, established under Part IIA of the Environmental Protection Act 1990), while the Pollution Prevention and Control policy is designed to prevent new contamination. Under these, and waste management licensing policies, a duty is placed on local authorities, as the primary regulators, to carry out inspections for the purpose of identifying contaminated land within their areas and to take action to secure its remediation.

The National Air Quality Strategy (Defra 2007a) recognises that policy to manage UK air quality needs to focus on different scales, depending on the nature of the sources and pollutants. These range from regulation of the local impacts of large point sources, to urban scale management, to national policies, and to European and hemispheric scale measures for pollutants with long transport distances, such as O3. However, the primary focus of the National Air Quality Strategy, and local air quality management, is to reduce human exposure to pollutants, rather than to protect ecosystem services. At all these spatial scales, the focus of UK policy has been measures to reduce emissions from sectors such as transport, energy production and industry, rather than through changes in ecosystem management. Hence, while there is widespread recognition of the co-benefits of measures to reduce emissions of both air pollutants and glasshouse gases to the atmosphere (Defra 2010), the linkages through changes in ecosystem processes and services have not yet been fully integrated into policy analysis.

Of more direct relevance to the protection of ecosystem processes and services are the air quality management policies implemented in the UK to meet the requirements of the Gothenburg Protocol of the Convention on Long-Range Transboundary Air Pollution (CLRTAP), which is currently being renegotiated, and associated EU directives, such as the National Emissions Ceiling Directive (UNECE 1999; EC 2010). This reflects the transboundary transport of the air pollutants with greatest impacts on ecosystem processes and services, namely, sulphur and nitrogen deposition and O3. The basis for the emissions reductions agreed by individual countries within this policy framework has primarily been optimising reduction of the exceedance of critical loads and levels. In terms of an integrating approach to ecosystem services, it is important that critical loads for acidification and eutrophication, in particular, have been explicitly set to protect adverse effects on soil and water quality, and the regulating services they provide. Furthermore, the models used to estimate these critical loads include regulating terrestrial ecosystem processes, including base cation weathering, sulphur and nitrogen retention and organic matter mobilisation, that show large spatial variation across Europe. Hence, the critical load method involves an integrated approach to air, soil and water quality regulation.

However, measures to reduce emissions of air pollutants impact more widely on soil and water quality regulation than through the factors considered in critical load assessments, and also affect climate regulation and provisioning services via a number of mechanisms that are identified in Tables 3, 5 and 6. Hence, air pollution legislation has potentially significant impacts (including both synergies and trade-offs) for a broad range of regulating and provisioning ecosystem services, as well as important interactions with other policy areas, particularly in relation to land management. This clearly highlights the complexity of anthropogenic impacts on different ecosystem services, and the need for a holistic policy approach.

In the case of ammonia emissions, 92% of which can be attributed to land management in the UK (Misselbrook et al. 2011), there has been a stronger emphasis on ecosystem management. Some of this has been achieved through the control of emissions from large pig and poultry enterprises by the national implementation of the EU Integrated Pollution Prevention and Control directive (European Commission 1996). In addition, the National Ammonia Reduction Strategy System model, used to inform policies to meet national emissions ceiling targets for ammonia in the UK, identifies changes in fertilizer use and application methods, livestock numbers, and livestock diet as factors contributing to a gradual decline in emissions since 1990 (Misselbrook et al. 2010); all of these management changes will also influence soil and water quality and climate regulation.

These policies for the national ammonia strategy form only one small element of a cascade of effects on ecosystems and wider society that result from primary emissions and ecosystem/atmosphere exchange of nitrogen oxides and ammonia. Recognition of these complex interactions has led the CLRTAP to establish a new Task Force on Reactive Nitrogen (Defra 2010; Misselbrook et al. 2010; TFRN 2010) to develop air pollution policies in the context of a full analysis of the nitrogen cycle. Interestingly, the 1999 Gothenburg Protocol already identified that ‘measures to reduce the emissions of nitrogen oxides and ammonia should involve full consideration of the biogeochemical cycle…and not increase emissions of nitrous oxide’ (UNECE 1999). Assessment tools have now become available that allow the implications of policy measures for nitrogen to be assessed at an ecosystem scale in an integrated and holistic way, including air, soil, water and climate regulation inter alia. For example, the recent European Nitrogen Assessment (Sutton et al. 2011) identifies new tools to integrate the management of nitrogen in soils, water and air, and the associated links to climate regulation. This approach allows the identification of policies such as improved nitrogen use efficiency, increased energy efficiency, reduced societal use of energy and transport and decreased animal protein consumption, which would have widespread benefits for a range of ecosystem services at a European scale (Oenema et al. 2011). Likewise, at a landscape scale, integrative models can allow the effects of the spatial linkages between managed and unmanaged ecosystems, hydrological flows and emission sources to simulate the effects of different policies on nitrogen flows through soil, air and water across the landscape (Dragosits et al. 2006; Duretz et al. 2011).

Even policy that is not aimed primarily at protecting the wider environment may also impact upon ecosystem service provision, and use ecosystems to deliver its aims. For example, present policies for the historic environment in Scotland, under Scottish Historic Environment Policy (Historic Scotland 2011), address soil as the neutral matrix in which artefacts and environmental evidence are embedded, over and into which buildings and sites are constructed, and which in time comes to seal sites, which have been destroyed or have decayed. The preferred approach for important archaeological sites and deposits is ‘preserve in situ’, which generally accords well with soil conservation objectives. For archaeological sites located in peat deposits, maintenance of a high water table is critical for the preservation of organic materials, and again this accords with other environmental objectives, notably climate and water quality regulation.

As described in this section, air, soil and water quality may sometimes be governed, or affected by, the same legislation, but sometimes the legislation is quite different. There are examples where policy delivers benefits to more than one ecosystem service, but there are others where benefits to one ecosystem service can harm another. Several policies and legislation addressing air, water, soil and climate are disconnected with no integrated overview of how these policies interact on the ground. This leads to conflicting messages regarding the use and management of ecosystems to deliver soil, water and air quality and climate regulation. However, there are more similarities and synergies associated with different forms of environmental legislation (climate, soil, air and water) than between the environmental legislation and the regulation of conservation and biodiversity. There are also potential trade-offs between policies to regulate soil, water and air quality, and climate and those for the regulation of conservation and biodiversity that need to be taken into account.

Future needs

This study considers only four of the regulating services from the full range provided by ecosystems (Smith et al. 2011). When one considers that there are multiple other supporting, provisioning and cultural services (UK National Ecosystem Assessment 2011), and that even a single ecosystem service is comprised of multiple facets, the enormous range of disciplines and expertise necessary to perform an ecosystem service assessment becomes clear. An ecosystem service approach allows seemingly disparate sectors and disciplinary knowledge to be brought together in a common conceptual framework (Millennium Ecosystem Assessment 2005; UK National Ecosystem Assessment 2011), and for the synergies and trade-offs to be considered together, even if a common metric (e.g. cost/benefit) is not possible for all services (Bateman et al. 2011). To make an ecosystem service approach work, however, multidisciplinary teams are essential. Future research should focus on developing multidisciplinary understanding and methods for working.

As noted in section ‘'Policies affecting the regulation of climate and soil, water and air quality by ecosystems'’, policies and aspects of legislation addressing air, water, soil and climate are increasingly integrated, but some remain disconnected. This can lead to conflicting messages regarding the use and management of ecosystems to deliver soil, water and air quality and climate regulation. At present, the financial returns, and hence local decisions, regarding rural land use in the UK are still primarily driven by the delivery of provisioning services such as food and fibre. Although there is a general appreciation of the importance of regulating ecosystem services, interventions by society and policy-makers to support such services are likely to be more economically, environmentally and socially sustainable if there is a clear understanding of the key interactions and of the potential scale of benefits. By adopting an ecosystem service framework, policy-makers may be better able to understand the implications of policy on a range of ecosystem services, and to better assess and foresee potential policy synergies and trade-offs. The Natural Environment White Paper for England is a good example of where an ecosystem service approach has been adopted for use in policy making (Defra 2011b). In section ‘'Synergies and trade-offs between actions to regulate climate and soil, water and air quality'’, we outlined some policies that were designed to impact one particular ecosystem service, but that had implications (either beneficial or detrimental) to other services. By identifying the synergies and trade-offs (as with the examples explored in section ‘'Synergies and trade-offs between actions to regulate climate and soil, water and air quality'’), ‘win–win’ options can be identified at the outset, so that policy-makers can develop policy with multiple benefits in mind. Where there are clear trade-offs, different stakeholders can be consulted to find acceptable solutions to address these trade-offs, or additional mitigation can be put in place to offset any negative impacts. Regulators, policy-makers, ecosystem managers, and more generally society and the wider environment stand to benefit from the use of an ecosystems approach, to deliver more coherent ecosystem management strategies.

Acknowledgements

This study builds on work conducted for the UK National Ecosystem Assessment (UK NEA), which received some support from UK NEA partner/sponsor organisations. The work of PS on this study contributes to Scotland's ClimateXChange. PS is a Royal Society-Wolfson Research Merit Award holder.

Conflicts of interest

The authors have no conflicts of interest to declare.

Ancillary