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The main research questions emerging from this meeting are: how will the climate change? How will the physical environment and vegetation change? How can predictive models of birds be improved? How important are extreme events? How can complexity be dealt with? Can we also predict increases? How will non-native species respond? Will species adapt? What is the effectiveness of current coastal conservation measures? Some of the main policy responses raised at the meeting were: adopt long-term plans, reduce other stresses; reconsider the status quo; create habitats; change public perceptions towards natural ecosystems; take potential problems associated with non-native species more seriously; convince policy-makers of the scientific realities; and consider the establishment of a panel on biodiversity change.

The BOU meeting on climate change and coastal birds, on which this Ibis special issue is based, was highly unusual in that it was probably the first ever BOU meeting in which after three-quarters of a day of talks there had been no mention of birds. The conference succeeded in bringing together researchers and policy-makers from a wide range of perspectives to create a stimulating meeting. For this summary I will concentrate on two issues: what are the future research questions, and what are the possible future policy responses? I will not, however, attempt to provide a complete shopping-list of possibilities but will focus on the issues raised at the meeting.

RESEARCH QUESTIONS

  1. Top of page
  2. RESEARCH QUESTIONS
  3. POLICY RESPONSES
  4. Acknowledgments
  5. REFERENCES

How will the climate change?

There is excellent evidence for the increased concentrations of CO2 and for increased temperatures with warmer summers and less cold winters (Watkinson et al. 2004). The main mechanisms by which global warming and sea-level rise occurs are also well accepted. There is, however, greater uncertainty over the timing and extent of warming and there are currently a range of predictions (Watkinson et al. 2004). This uncertainty becomes greater when considering local predictions. There is intense global research to refine and validate our existing understanding and predictions, and this is obviously essential information. The International Panel on Climate Change (IPCC) is widely acknowledged as being an excellent example of how to bring together scientists with conflicting beliefs, data and models to create a consensus view while still acknowledging areas of uncertainty and dispute.

The fine detail as to precisely how the climate changes may well be critical. For example, Piersma and Lindström (2004) describe the importance of wind systems to migration systems, so that seasonal changes in the direction of winds could have serious consequences for those birds that migrate. Similarly, predicting the frequency of extreme events, such as severe weather, is probably important, but extreme events are notoriously difficult to predict.

How will the physical environment and vegetation change?

Many papers in this special issue raise the difficulties associated with predicting habitat changes, such as those relating to hydrology and sedimentology (Crooks 2004, Hughes 2004), which are likely to have impacts particularly on saltmarsh (Knogge et al. 2004), and temperature and vegetation changes to tundra (Piersma & Lindström 2004). A critical issue is the time lag: whether the responses take place over years, decades or centuries is of considerable conservation importance. Such information is obviously essential as habitat change represents the intermediate stage between climatic responses and the responses of birds. The isostatic lowering of land (e.g. in southeast England) provides one opportunity to study coastal changes that might also occur as a result of climate change. Hughes (2004) describes how, in some areas, saltmarshes have accreted even in the presence of isostatic lowering, thus resulting in the land being relatively higher than the sea. Determination of historical patterns of pollen abundance of tundra species in response to previous climatic change is another obvious approach to predicting responses of tundra vegetation to anticipated climate perturbations.

How can predictive models of birds be improved?

Norris et al. (2004) describe how predictive models have been successful in answering a wide range of questions relating to climate change (e.g. Percival et al. 1998). As they point out, behaviour-based game theory models have the strength that they can be used for considering population ecology under novel conditions. Conventional models often cannot deal with conditions outside the range in which the parameters and biological processes were determined. Producing predictive models has the advantage of considering the likely magnitude of responses and in identifying areas of ignorance. However, as Norris et al. (2004) state, there is a need to consider wider spatial scales and to link physical models of coastal environments to ecological models.

How important are extreme events?

Extreme cold winter events are important due to the direct impact on birds and the direct and indirect impact on their prey (Watkinson et al. 2004). Understanding the long-term demographic impacts of occasional extreme events is important to predict what would happen if these events become less or more frequent. Are the consequences just local and short term or are populations typically reduced over longer periods as a result of such occasional extreme events?

How can complexity be dealt with?

In the talk that provided the basis for his paper, Theunis Piersma introduced the concept of the horrendogram: a complex interacting web of factors, many of which are poorly understood. As he pointed out, there is often a hierarchy of questions. Will the local sea-level rise? Will the sediment respond to any change? Will the vegetation respond to any sediment change? How will the prey and vegetation respond?

As examples from this special issue, Kendall et al. (2004) suggest that many of the impacts of climate change on the invertebrate prey will depend upon the consequences of changed temperature upon fucoid algae, which would otherwise protect certain prey species living within from desiccation. They also point out that any decline in algae will reduce the quantity of decaying algae on the strandline, leading to reductions in the populations of invertebrates and the birds that feed upon them. Similarly, Croxall (2004) describes the complexities of predicting the consequences of change within the relatively simple Antarctic system, where changes in a single physical variable, e.g. the extent of sea ice, can have opposite effects at different stages of the breeding and life cycles of pagophilic species. Piersma and Lindström (2004) describe how various predictive models have suggested how much tundra and sea ice (which cools the surrounding land) would be present in the future. What would be the consequences of various combinations?

Making predictions within such a maze of uncertainty is clearly difficult and there is a need to develop novel means for doing so. It is often not possible to demand that further research is undertaken before decisions are made because policy-makers often have to make decisions to act (or not act) now. It is probably sensible to find the best means of contributing to the debate with whatever data and understanding there are, while stressing the uncertainty and need for further work.

Can we also predict increases?

It is generally easier correctly to predict population declines than population increases. The reason is that it is relatively easy to predict whether changes to some aspects of a habitat make it unsuitable, but much harder to predict if all aspects of habitats will become suitable. A UK example would be that climate warming in the uplands is very likely to result in a loss of habitat for Eurasian Dotterel Charadrius morinellus and Snow Bunting Plectrophenax nivalis, but it is much harder to predict whether Kentish Plovers Charadrius alexandrinus, Collared Pratincoles Glareola pratincola and Black-winged Stilts Himantopus himantopus will increase as it is likely to depend upon the responses of their potential prey, parasites, competitors and predators.

How will non-native species respond?

Non-native species are already a serious problem worldwide, having a significant negative effect on the world's biodiversity (Williamson 1996). In the UK an unexpected problem was the loss of coastal habitat resulting from the crossing of native and introduced cord grass Spartina species. An under-considered issue is the likely response of numerous non-native species to changes in temperature and rainfall. Two bird species are of current concern in the UK: will climate change facilitate the continued expansion of the Rose-ringed Parakeet Psittacula krameri in southeastern England, and will it enable the House Crow Corvus splendens to reach Britain from its foothold in The Netherlands – both species have the potential for biodiversity and economic impacts (Feare 1996, Ryall 2002). As yet, it is very difficult to predict which species are likely to become established and increase, and the consequences of them doing so (Sol et al. 2002).

Will species adapt?

The most optimistic scenario is to assume that species will simply evolve to adapt to the changed conditions and thus that there will be minor changes in population sizes. There are a number of examples of responses. Eight out of nine species of common wintering UK waders have changed their wintering areas by moving north or east to what are traditionally colder regions (Rehfisch et al. 2004), birds are breeding earlier (Crick 2004) and there are indications of some changes in the phenology of migrants (Sparks & Mason 2004), although in their analysis, Sparks and Mason showed results were often contradictory and inconclusive. Similarly, there might be other species that may fail to respond. The alternation of the relationship between temperature and photoperiod may affect the timing of breeding of certain intertidal invertebrates (Lawrence & Soame 2004) and it is unknown how rapidly such prey of coastal birds may be able to respond.

As Piersma and Lindström (2004) state, 16 000 years ago Western Europe was covered in an ice sheet and thus the current migration routes must have evolved since then. Short-distance migrants may be able to respond to climate change more readily. A possible consequence is that short-distance migrants and residents may outcompete long-distance species. The greatest concerns may thus be for long-distance migrants with competitors that are short-distance migrants or residents.

In a review of the evidence, Sutherland (1998) showed that many bird species have changed migration routes in response to changed environmental conditions. Many others, however, have migration routes that suggest that they have been unable to evolve more sensible routes. It is possible that the ability to respond to climate change is erratic and will depend upon genetic details, which may be difficult to predict (Dolman & Sutherland 1995).

Crick (2004) raised the issue of miscuing, in which birds return earlier because of improved conditions on the wintering grounds or during migration, but arrive in the breeding area before conditions have become suitable there. Alternatively, birds may miscue by failing to respond where changes of timing would be beneficial. Understanding what determines which species will be able to respond will improve the ability to predict the response of populations.

What is the effectiveness of current coastal conservation measures?

A common problem with habitat management is that we do not learn from previous successes and failures (Sutherland 2000). Atkinson et al. (2004) showed that the success of managed retreat schemes varies considerably but that there is no history of testing these schemes. There is a clear need to change attitudes to nature conservation in order to record experiences and provide a basis for evidence-based conservation.

POLICY RESPONSES

  1. Top of page
  2. RESEARCH QUESTIONS
  3. POLICY RESPONSES
  4. Acknowledgments
  5. REFERENCES

Adopt long-term plans

There is a clear need to adopt long-term plans (Knogge et al. 2004) in order to find cost-effective means of reducing the greatest effect of climate change. These need to consider the changing requirements for water and energy (Holliday 2004). However, discounting means that the current value of long-term benefits is very low, which is one reason why politicians are reluctant to, say, reduce fisheries catches even though there will be long-term benefits. The greater the discounting, the greater the reluctance to think in the long term (Henderson & Sutherland 1996). Particularly high discount rates result from poverty or political instability. Thus areas with the greatest need for long-term planning may be the least likely to achieve it.

Reduce other stresses

Croxall (2004) points out that for marine systems it is unrealistic to expect any management in the form of mitigation, so that the priority must be to ensure that the systems are managed in a sustainable manner to reduce the impact of compounding effects. Similarly, those US states that are heavily agricultural (intensively farmed?) have lost over 80% of their historical wetlands, and thus there is reduced capacity for change (Zedler 2004).

Reconsider the status quo

Climate change may require the rethinking of many aspects of conservation, some of which, such as the EU Habitats and Species Directive, are fundamental to the current thinking of conservationists (Boere & Taylor 2004, Crooks 2004). Conservation policy has usually depended upon maintaining the status quo. In-kind mitigation, whereby loss of one patch of habitat requires the restoration of an additional area, is a huge advance. However, conservation areas may have to be more fluid in the long term, both as species and communities are affected by climate change, but also because of physical changes to the environment

Create habitats

Climate change will result in a range of problems resulting from sea-level rise, increased flood risk, and change in water supply and requirements. Habitat creation and restoration may act to help solve some of these problems, even though habitat restoration is not always straightforward and often differs in quality to the lost habitat (Zedler 2004). For example, managed realignment may be much more cost effective than defending sea walls. Similarly, protecting watersheds and restoring floodplains may help to reduce flooding downstream. Within the current thinking regarding agriculture in Western Europe, it is sensible to reconsider how agricultural subsidies are spent and whether some of the subsidies could be redirected to habitat restoration (Sutherland 2002). This could have benefits to a wide range of functions, including tourism, recreation, increased quality of life and hunting.

Change public perceptions towards natural ecosystems

A major problem in the debate over the future of the countryside is that unmanaged land is often considered derelict. Any attempt to restore natural ecosystems on a large scale is likely to have to be accompanied by a public-relations and education programme.

Take non-native species more seriously

Climate change is likely to result in numerous surprises as non-native species suddenly become problems. An obvious solution to this is to take the control of non-native species far more seriously.

Convince policy-makers of the scientific realities

As with many developing scientific issues, there is healthy debate and disagreement about the likely magnitude of climate change. Policy changes are only likely once politicians have accepted that it is worth acting. This will require a combination of further research to reduce uncertainties and effective dissemination.

Consider the establishment of a panel on biodiversity change

It may be useful to establish a panel, equivalent to the IPCC, to review and promote research into existing climate change impacts on biodiversity and to predict expected changes. The IPCC has been very effective by bringing together conflicting views.

Acknowledgments

  1. Top of page
  2. RESEARCH QUESTIONS
  3. POLICY RESPONSES
  4. Acknowledgments
  5. REFERENCES

I thank Mark Rehfisch and Chris Feare for inviting me to the meeting to give this summary and for providing useful comments, John Croxall for useful policy suggestions, the BOU for organizing the meeting and the speakers and discussants for providing stimulating material for me to raid.

REFERENCES

  1. Top of page
  2. RESEARCH QUESTIONS
  3. POLICY RESPONSES
  4. Acknowledgments
  5. REFERENCES