Common themes for ecologists in global issues


  • Robert Watson

    1. Environmental Director of the World Bank, and Chairman of the Inter-governmental Panel on Climate Change Director, Environment, The World Bank 1818 H Street, NW, Washington DC 20433, USA
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Robert Watson, Director, Environment, The World Bank 1818 H Street, NW, Washington DC 20433, USA (e-mail:

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It is a real pleasure to be here today as a non-ecologist speaking to so many ecologists. I would like to show how ecology is absolutely central to everyday living. We need to link the type of detailed work you do with the policy makers in London, Washington DC and various capitals around the world. I would like to put this in the context of sustainable development.

The development challenge

We need to alleviate poverty: 1·3 billion people live on less than a dollar per day, the cost of half a pint of beer; 3 billion people, i.e. half the world's population, live on less than 2 dollars per day; 800 million people are malnourished today, especially in Africa. Furthermore, 1·3 billion people have no clean water, a major health threat; 2 billion people live without sanitation; 2 billion people have no electricity and obtain their heat and cook their food by burning dung and biomass, leading to incredible levels of indoor air pollution that result in early death and miserable lung disease; 1·4 billion people are exposed to extremely unhealthy air outside, again because of burning biomass. Alleviation of these appalling conditions underlies the challenge of development and the elimination of poverty, which is the primary role of the institution at which I work: the World Bank.

Meeting our basic human needs of food, energy and clean water using current practices is leading to environmental degradation at the local, regional and global scale; and as the environment degrades it becomes more difficult to meet those basic human needs. It is an unsustainable cycle. For example, to meet the ever-increasing global food supply requirements, we have either irrigated our lands, increased the amount of land used for farming, that is to say cut down our pristine forests (expanded the area of agricultural production), or increased the use of nitrogen fertilizers (intensified agricultural production). Each of these three approaches is to some degree leading to environmental degradation. Irrigation in many parts of the world has led to the salinization of soils and a loss of soil fertility, resulting in a loss of agricultural productivity. And as we cut down our forests, especially using unsustainable slash-and-burn agricultural techniques in the tropics, we are causing a significant decrease in the amount of primary forest, which is leading to a loss of biological diversity at the species and genetic level. A loss of genetic diversity threatens the long-term security of our food supply because of the loss of wild relatives, which we may well need in the future. In addition, cutting down our forests leads to a significant emission of carbon dioxide into the atmosphere. Furthermore, excessive use of nitrogen fertilizers has increased the atmospheric concentration of nitrous oxide, also a greenhouse gas. Today, about 6 billion tonnes of carbon are emitted into the atmosphere from the combustion of fossil fuels and 1·6 billion tonnes of carbon from unsustainable agricultural and forestry practices. Also, the methane cycle is being changed. Emissions of methane have increased in part because of rice production and cattle rearing. Changes in nitrous oxide, carbon dioxide and methane, all greenhouse gases, are contributing to a significant change in the Earth's climate. Changes in temperature and precipitation patterns are projected to lead to significant regional changes in agricultural production. Later, I will show that this will probably lead to an increase in agricultural production in the middle and high northern latitudes, and a very significant decrease in production in the tropics and subtropics where there is hunger and famine today. The basic problem is that the practices we use today to meet our basic human needs are clearly unsustainable.

Scientific linkages

There are seven global environmental issues for which there are either international conventions or principles agreed at Rio at the Earth Summit in 1992:

• climate change;

• loss of biological diversity;

• desertification and land degradation;

• stratospheric ozone depletion;

• deforestation and unsustainable forestry;

• degradation of fresh and marine waters;

• persistent chemicals that disrupt the hormone system, the ‘so-called’ endocrine disrupters.

One problem is that most scientists and policy-makers address these environmental issues in isolation. This is a mistake because they are highly coupled, both from a scientific and policy perspective. The optimum approach to deal with these issues is to understand the scientific linkages among them. Then effective policies, practices and technologies can be developed and implemented to address simultaneously each of these issues while meeting a basic human need.

Let me briefly examine some of the linkages among these issues. For example, a change in the Earth's climate will have a significant effect on the structure and functioning of ecological systems and hence on biological diversity. A warmer world will result in the boundaries of ecological systems moving polewards and to higher elevations. Changes in the structure and functioning of ecological systems will change the cycling of key nutrients within these ecological systems, thus feeding back on the climate system by changing the sources and sinks of key greenhouse gases. In addition, as the Earth's climate warms, the vertical temperature structure will change, affecting stratospheric ozone, which in turn affects the amount of ultra-violet radiation that reaches the Earth's surface; this again will have an impact on biological diversity. Furthermore, loss of stratospheric ozone, itself largely caused by chlorine- and bromine-containing compounds (chlorofluorocarbons and halons), changes the temperature structure of the atmosphere and hence can modify the Earth's climate.

Changes in the Earth's climate can also have a major effect on land quality. Changes in the Earth's climate caused by an increase in greenhouse gases will not only alter temperature patterns but, even more importantly, there will be significant changes in the spatial and temporal patterns of precipitation, and because of the higher temperatures, there will be changes in evapo-transpiration. These will result in changes in run-off at the local and regional scale. Most climate models suggest that in a warmer world the arid and semi-arid areas of the world will become even more arid and semi-arid, further exacerbating the effects of poor land-use practices. In turn, desertification changes the albedo of the land, hence influencing climate at the regional level.

Changes in climate are projected to have major effects on the world's forests. In a world where the atmospheric concentration of carbon dioxide has doubled, many ecological models suggest that one-third of all tree species would change: one-seventh of the tree species in the tropics, and two-thirds of the tree species in boreal systems. One of the most important questions facing us is, given the rapid rate of climate change projected by the climate models, can tree species adapt or will there be a significant die-back in tree species?

It is clear that we should not be looking at each of these environmental issues in isolation, but as a series of coupled issues. And we must recognize that each of these environmental issues is affected by, and/or affects, what society cares about most: a healthy environment and the supply of food, energy and water. Therefore, the challenge for the scientific community is to understand this highly interlinked system, and to explain it in an understandable manner to the key policy-makers in London, Washington, Beijing and Delhi, so that they can make effective use of our scientific knowledge. At the end of the day, policy formulation will be only as good as the scientific knowledge we provide. Therefore, it is important to realize that we cannot use a disciplinary approach for these complex issues, but we need to use an interdisciplinary and multidisciplinary approach, with ecologists working together with physicists, chemists, meteorologists, oceanographers, mathematicians, economists, social scientists, etc. The challenge is simple: we need to study these issues in a holistic manner if we are to realize the vision of sustainable human development.

Current trends and underlying causes of changecm

It is evident that human activities are changing the environment at the local, regional and global scale. At the global scale the Earth's climate is warming, biological diversity is being lost, the stratospheric ozone layer is being depleted and water and land resources are being degraded. Let me briefly examine the current trends in biological diversity and the underlying causes of change. It is very clear that human activities are changing the landscape through the expansion of agricultural systems, urban environments and roads at the expense of natural habitats. During the last 400 years there is a documented extinction, which is almost certainly an underestimate, of nearly 500 animal and 700 plant species. If we assume that the average life span of an individual species ranges from 5 to 10 million years, this means the current rate of species extinction is 50–100 times the natural background rate. Therefore, it is clear that over the last 400 years humans have already had a marked effect on the Earth's biological resources.

Biological diversity is being lost because of the:

• fragmentation of natural habitats;

• conversion of natural habitats;

• over-exploitation of wild resources;

• introduction of exotic species;

• air and water pollution; and

• climate change

The underlying causes for this loss of biological diversity, include the following.

1.Increased demand for biological resources due to an increasing population and economic wealth. Since 1950, there has been a 40% increase in per capita demand for grain, 100% in fish and 33% in wood. In addition, the Earth's population has increased substantially since 1950, giving a double impact on our natural resources. Unless we change our current practices and technologies during the next 10–25 years, there may have to be major declines in per capita use of fish, crop-lands, forest and irrigated lands. This will prove to be a major challenge for some countries, including China, which has one of the largest populations in the world, and one of fastest growing economies, but some of the lowest per capita natural resources, whether arable land or freshwater;

2.Markets have failed to recognize the true value of biological diversity, and to allocate the appropriate global value at the local value. Markets recognize the value of food, biomass for energy, pharmaceuticals for health and ecotourism. However, they do not recognize the importance of ecological services that provide the very foundation for sustainable development and human welfare, i.e. purification of air and water, stabilization and moderation of the Earth's climate, moderation of floods and droughts, moderation of temperature extremes, generation and renewal of soils and soil fertility, dispersal of seeds, pollination of plants, and control of pests. Nor do markets recognize the option value, the undiscovered drug, the undiscovered wild relative of an agricultural product we might need in the future, the existence value of biological species, and the cultural, religious and aesthetic value of biological resources. Techniques such as contingent valuation can be used to estimate the aesthetic, cultural and existence value of biodiversity. However, until a value is placed on ecological services, we are likely to continue to lose them. Bob Costanza (1997) and a few other ecologists have attempted to estimate the economic value of the Earth's ecological services. They estimated the total value at 33 trillion US dollars per year. Many economists argue that their estimates are almost certainly wrong. However, it does not matter if Bob and colleagues are right or wrong, the value is almost certainly very high. One important value of the world's forests, especially the tropical forests, is the high carbon content – up to 200 tonnes of carbon per hectare. One approach to protecting the climate system is through the reduction of emissions from energy systems. A complementary approach is the sequestering of carbon in ecological systems. Experts estimate the value of carbon at between 5 and 100 dollars per tonne. Thus, at 20 dollars a tonne, the carbon value of tropical forests is about 2000 dollars per hectare. Hence, one of the best ways of protecting tropical forests is to create a market to buy and sell carbon. The World Bank is currently developing a fund for trading carbon.

3.Institutional failures to regulate biological resources. For example, fisheries are collapsing all over the world, not due to a lack of knowledge about fisheries, but due to lack of functioning institutions.

4.Inappropriate use of technologies, sometimes totally inadvertent, sometimes purposeful. A good example of an inadvertent use of a technology that resulted in environmental degradation was the use of chlorofluorocarbons (CFCs) as refrigerants, foam-blowing agents, and solvents. CFCs are non-toxic gases and therefore safe to use in the house. Unfortunately, they destroyed stratospheric ozone, leading to an increase in ultra-violet radiation reaching the Earth's surface, with adverse effects on ecological systems and human health, through melanoma and non-melanoma skin cancer, eye cataracts and a possible suppression of the immune system. However, once the scientific community demonstrated that CFCs were destroying stratospheric ozone, governments continued to allow CFCs to be emitted into the atmosphere for probably a decade longer than they should have. Governments have now banned the production and consumption of most ozone-depleting gases. However, even with this ban, ozone depletion will continue until well into the middle of the next century with resultant increased levels of ultraviolet radiation reaching the Earth's surface.

5.The failure of people to care about tomorrow. Most people care about today and do not worry about the long-term consequences of their actions; they do not think about the environment that they will leave for their children, let alone their grandchildren or great grandchildren.

6.Human migration, travel and international trade. Clearly, these are not scientific issues alone. There is a need to couple the natural sciences with economic and social issues. Until we do, the scientific community cannot expect to influence the policy-makers of the world. A common question asked by policy-makers is ‘what are the costs of actions to protect the environment, and what are the costs if we don’t take action to protect the environment?’ Consequently, we need to discuss biological diversity and ecological processes within a social and economic framework, hence the importance of valuing ecological services and creating and using markets to protect biodiversity. The type of research you do every day contributes to our understanding of one or more of these ecological services, and it is understanding these ecological services that is so crucial. There is a need to understand the relationship between the structure and functioning of ecological systems. For example, we need to understand how many species can be lost before functions are lost or changed. These are some of the questions that it is so critical to answer in order that there can be wise management of the ecological systems.

Measuring the wealth of a Nationcm

A true measure of the wealth of a Nation should include four components:

• produced assets or industrial capital;

• human resources, including education and health;

• natural capital, including renewable (e.g. forests, wetlands and coral reefs) and non-renewable resources (e.g. oil reserves);

• social capital, including the value of social systems.

In OECD countries, such as the United Kingdom and the United States, nearly all of their value is in their human resources rather than built and natural capital, i.e. it is in human intellect and social institutions. But in many developing countries, clients of the World Bank, a much greater percentage of their wealth is in natural capital.

Unless rates of change in natural capital and the social costs of environmental degradation are taken into account when the wealth of a nation is calculated, significant errors are likely. For example, if the savings rate for a country such as Mexico (late 1980s) are calculated without taking into account the depletion of natural resources and environmental degradation the economic situation of the country looks in good shape (10–15% real savings rate). However, if allowance is made for forest degradation and depletion of oil reserves, the savings rate goes down to about 5%. Furthermore, if allowance is made for the degradation of water and air quality it results in a calculated negative savings rate. Fortunately, some of the oil revenues were used in developing human capital, via an improved education system, hence an increase in human capital. A key question that is often asked is to what degree are different forms of capital exchangeable in a sustainable world? A decrease in natural resources may not always be bad, for example if it is used for the education. The basic point is that the depletion of natural resources and environmental degradation must be taken into account when calculating the wealth of a Nation, otherwise one over-estimates the value. Unfortunately, most developed countries, including the UK and US, do not routinely take into account changes in all forms of capital when estimating their wealth.

One often-asked question is: ‘Why should a poor land-less peasant not cut down a tree to sell or use for fuel wood?’ In many instances the answer is that he should because he probably has very few opportunities to make money. A poor land-less peasant has a very short time horizon and very few choices and has to take whatever opportunities come his way to eke out an existence day to day. Therefore, a major challenge is to create and use markets so that there is an economic incentive for the land-less peasant not to cut down his tree.

So there are two challenges. The first is to understand the value of biological resources and ecological services. The second is to create markets that will give a real incentive for the land-less peasant to do the right thing.


The frontier forests of the world are rapidly being lost. Of the frontier forests in Russia and Europe, only about 3·5 million km2 are left out of what was once 16 million km2. In Asia, less than 1 million km2 remain out of 15 million km2. South America has the largest percentage of original frontier forests remaining, probably around 50%. Tropical forests are rich in biological diversity, hence the recognition that it is essential to protect them. However, it is equally important to protect the temperate and boreal forests in Russia, which are also susceptible to ecological and environmental changes. Logging, mining, oil exploration and agricultural clearing are the major threats to frontier forests. At least 40% of all frontier forests today are under threat. In Africa, probably 80% are now under threat, in Oceania all of it, and in Central America 90% of it.

The current rate of loss of tropical forests is unsustainable. During the last decade 11% of tropical forests in Asia have been lost, 8% in Latin America and 8% globally. The overall rate of loss of forested land has been partially offset by an increase in plantation forests. Much of the former frontier forests have gone into arable land. The loss of frontier forests is leading to a rapid loss in terrestrial biological diversity: 5–20% of identified species are already threatened, and are almost certain to become extinct whatever we do. If closed tropical forests continue to be destroyed at the current rate of about 1% per year over the next 30 years an eventual additional 5–10% loss of species is projected. This would be a rate of extinction of 2000–5000 times the natural extinction rate. Experts have suggested that we are on the verge of the next great extinction, the first ever to be caused by human activities. We are losing not only species, but also populations and genetic variability; the latter could be absolutely crucial as the environment changes, especially the Earth's climate.

We are clearly witnessing a major loss of biodiversity at the species level, the ecosystem level and the genetic level just because of land clearing. Global warming, when coupled with these other human pressures on natural habitats, will accelerate loss of biological diversity even further.

Climate change

There is now no doubt that human activities are changing the atmospheric concentration of the greenhouse gases due to energy and land-use practices. In some regions of the world the atmospheric concentrations of aerosols are increasing as a result of the combustion of coal and slash-and-burn agriculture. Greenhouse gases warm the atmosphere, whilst aerosols cool the atmosphere. Greenhouse gases have lifetimes of 10–100 years, while aerosols have lifetimes of only a couple of days. Hence, the greenhouse gas effect is global, while the aerosol effect is regionalized.

There is no question that the Earth's climate is changing. Mean land and ocean surface temperatures have increased half a degree centigrade during the last 100 years, with land surface temperatures increasing 0·8 °C. Glaciers have retreated world-wide. Precipitation patterns are changing, and sea level has risen between 15 and 25 cm. The observed changes in temperatures cannot be explained by variations in natural processes alone, i.e. changes in solar variability, volcanic activity, and the natural exchange of energy between the ocean and the atmosphere. The general trend in global mean surface temperature is broadly consistent with climate models, which suggest that in a doubled CO2 world it will be 3–4 °C warmer. In addition, experts have compared the observed changes in temperature as a function of latitude and altitude with those simulated by models that take into account increased atmospheric concentrations of greenhouse gases, aerosols and stratospheric ozone depletion. To a first approximation, there is a good correspondence between theory and observation. Hence, the Inter-governmental Panel on Climate Change (IPCC) concluded that human activities are now having a discernible human influence on the Earth's climate.

Precipitation has changed throughout the world. It is getting wetter in Asia and most of Latin and North America. In contrast, Africa and parts of South-east Asia are becoming drier. Climate models predict that in the USA there will be more rain in winter and more rain should fall in heavy precipitation patterns [at least two inches (5 cm) in 24 h], with a decrease in light to moderate events [one-tenth of an inch to half an inch (3–13 mm) in 24 h]. Such changes would lead to more floods and more droughts. Furthermore, some models predict changes in the monsoon pattern in India causing more severe, long-lasting droughts, especially in summer; We are not sure what will happen to the frequency and magnitude of cyclones and tornadoes. Each of these projected changes in climate has major implications for managed and unmanaged ecological systems.

If governments do not agree to reduce the emissions of greenhouse gases because of climate change considerations, increases in population, economic growth, and energy practices will result in the atmospheric concentrations of CO2 increasing from today's level of 360 parts per million to somewhere between 500 and 1000 parts per million by 2100, leading to changes in temperature of 1–3·5 °C. That would be a rate of change in temperature faster than anything observed in the last 10 000 years. Changes in temperature will not be uniform with latitude. There will be increases of up to 5–10 °C in mid and high latitudes in the Northern hemisphere, with much smaller increases at high latitudes in the Southern hemisphere. Deep water forms in Antarctica, so the energy of the atmosphere is pulled down to very great depths in the oceans around Antarctica, thus slowing down increases in atmospheric temperatures. These changes in temperature would be accompanied by a sea level rise of 15–95 cm.

Global warming can be reversed only very slowly. Even if the global emissions of greenhouse gases were stabilized today, the atmospheric concentration of carbon dioxide would not stabilize for hundreds of years because of the very long time constants associated with carbon dioxide. Its atmospheric lifetime is governed by the rate of exchange between the atmosphere and the deep ocean. There is rapid exchange (a few years) between the atmosphere and the surface ocean, but the factor that controls the lifetime of carbon dioxide is the rate of exchange between the surface waters and the deep ocean. Even after the atmospheric concentration of CO2 is stabilized it takes decades to stabilize atmospheric temperatures. Once atmospheric temperatures are stabilized, it takes many centuries to stabilize sea level. Ecosystem restoration – if it is even possible in the first place – would take decades to centuries, and species loss is truly irreversible. We should also acknowledge that most forms of capital stock (automobiles, power plants, ports, roads) have long lifetimes. Therefore, to deal with climate change in an economically sensible way, we have to take into account the natural turnover rate of capital stock, i.e. years to centuries. The obvious implication of these long time constants for policy-makers is that they cannot wait for perfect knowledge. If they wait to see whether greenhouse gases do change climate, as all models predict, and they do not like the impact of that changed climate, it would take centuries to millennia to reverse the damage, even with a complete cessation in the emissions of greenhouse gases.

A simple calculation was done by the UK Meteorological Office. They allowed the atmospheric concentration of CO2 to increase at 1% per year for 70 years, then kept it level thereafter. The response of sea level was to rise monotonically for well over 1000 years. Once atmospheric composition is changed, an increase in sea-level is set in motion that cannot be reversed for millennia. There are clearly major implications for low-lying deltaic areas, mangrove swamps, coral reefs and small island states.

One of the key questions we have to ask ourselves is ‘Will a change in the Earth's climate lead to a change in ocean circulation?’ The classical ‘conveyor belt’ concept shows that warm water is transported near the surface from the Equator toward the north pole, where it gets subducted downward into the Arctic Ocean off Greenland. In a doubled- or a tripled-CO2 world, deep-water formation off Greenland will not occur or will significantly slow down. This could occur because an increase in the amount of precipitation in the North Atlantic would mean that the ocean would become less salty. This effect will be amplified by an increased run-off from Greenland. Thus, the north Atlantic ocean off Greenland will become less dense, both by being less salty and by being warmer because of global warming. Therefore, the water will not sink as quickly, disrupting a key part of the global circulation pattern. If there were to be a shut-off or a partial close down of the North Atlantic conveyor belt, it would not only have major implications for the climate in Europe, but also major implications for nutrient cycling and marine ecosystems.

The impact of climate change on human health and managed and unmanaged ecological systems

While these projected changes in climate are likely to benefit some regions, for most regions there will be significant adverse consequences on human health, ecological systems and socio-economic sectors. The primary challenge for ecologists is to quantify the impact of changes in temperature, precipitation and sea level (mean values, extremes and variability), in conjunction with increases in the atmospheric concentrations of carbon dioxide, on managed and unmanaged ecosystems. In addition to being concerned about the impact of climate changes on ecological systems, there is also a major concern about the impact of climate change on water resources, especially on arid and semi-arid lands, and the effects of sea level on human settlements.

It is important to recognize that climate change is an important new stress and that most ecological systems respond to both the rate and the magnitude of changes in climate. And developing countries are much more vulnerable than developed countries, because of lack of financial and institutional capacity. Unfortunately, our ability to project the implications of climate change at the regional level are limited because: (i) our ability to predict climate at a regional level is limited; (ii) some of the ecological processes are not particularly well understood; and (iii) the systems are subject to multiple stresses.

Human health

One of the major ecological challenges is to quantitatively understand the implications of changes in climate on the spatial patterns of vector-borne diseases, particularly malaria and dengue. Mosquitoes carry malaria and dengue fever. The potential range of mosquitoes and of the malaria parasite today is primarily in the tropics and subtropics. In a doubled-CO2 warmer world, it is expected to spread to higher latitudes in both the northern and southern hemisphere and to higher altitudes. Ecological models project an increase in the incidence of malaria from about 300 million cases per year to as many as 350–380 million cases per year in a doubled-CO2 world: the annual mortality rate would increase from 2 million to 2·5 million, primarily in the tropics. This disease primarily occurs in developing countries due to poor health care facilities. In developed countries such as the USA, which have good health care facilities, and where malaria was once endemic, malaria is not a serious problem. These projected increases in the incidences of malaria assume no significant improvements in health care systems.

Unmanaged ecosystems

Climate change and changes in the atmospheric abundance of carbon dioxide affect the structure, functioning and boundaries of ecological systems. In addition, alien invasive species may be favoured and there will be changes in productivity. It is important to recognize that different species/ecosystems respond quite differently to different climate variables. For example, mangrove systems are most affected by storm frequency and sea-level rise. Our current understanding of coral reefs suggest that they will not be threatened by an increase in sea level because they can accrete at a rate comparable to that at which sea-level is projected to rise, but they will be threatened by long-term, sustained changes in temperature. Periodically (every 2–7 years), significant coral bleaching events have been observed in many of the coral systems of the world in response to elevated oceanic temperatures caused by the El Ninō phenomena. The IPCC concluded that in a world that is 3–4 °C warmer, many – if not most – of the coral reef systems of the world would be highly threatened.

Forest systems respond to changes in both temperature and precipitation. Ecological models are being used to simulate the current distribution of potential vegetation from tundra to boreal forests, to savannas and shrublands. Unfortunately, there are relatively significant differences in the details of the model outputs, especially in high northern latitudes. Therefore, a major challenge is to improve these ecological models of potential vegetation. When ecological models are used to evaluate what would happen in a doubled-CO2 world, they typically project that there would be major changes in the extent of tundra and boreal forests, with a significant expansion of the extent of boreal forest once the climate has reached a new equilibrium. A critical question that needs to be answered is what will happen to tree species during the rapid transition from today's climate to that of a doubled-CO2 world. Answering this question will require coupling a transient climate model to a transient ecological model.

While there is a significant amount of scientific data, primarily collected under controlled conditions in greenhouses, on the response of monocultures to enhanced abundances of carbon dioxide, much less is known about the response of complex forested systems. The MAPS ecological model indicates that in a doubled-CO2 world there would be significant decrease in leaf area index if the CO2 fertilization effect is not taken into account. However, if allowance is made for the CO2 effect, the MAPS model predicts an increase in leaf area index. Hence, productivity is critically dependent on how the CO2 fertilization effect is addressed.

Different ecological models give different results, and driving them with different climate models also leads to different results. Examining the predicted changes in the vegetation patterns of the USA, there are significant differences using a single ecological model but driving it with three different climate models. In all three cases the models suggest that the potential vegetation of the east coast of N. America will primarily remain woodlands. However, in all three cases the models suggest that beech trees would no longer be viable on the east coast of the US. So, even though the east coast could remain a woodland system, the species composition would change drastically.

A key question is how climate change and increasing habitat disturbance will benefit invasive species. In addition, a significant increase in the frequency of fires is expected in tropical, temperate and boreal systems; that again may allow opportunistic species to invade. Independent of climate change, biological diversity around the world is threatened by exotic species. In mainland areas, 20% of mammals are currently being threatened by exotic species, as are 11% of mammals on islands. For birds, 5% are already being threatened by exotic species in mainland areas, and 40% on islands. Hence, one of the synergistic effects potentially detrimental to biological diversity could be climate change and the introduction of exotic species.

Species have clearly migrated very easily during previous periods of climatic change. However, the world today is very different. There were always mountains to act as natural barriers to the migration of species, but now roads, cities and agricultural systems act as man-made barriers to the migration of species in response to climate change. In order to protect natural ecological systems we are going to have to assist the migration of species through a system of biological corridors.


WP end marked textCurrently, 800 million people are malnourished, and as the world's population increases and incomes in some countries rise, food consumption is expected to double over the next three to four decades. Studies show that, on the whole, global agricultural production could be maintained relative to baseline production in the face of climate change under doubled carbon dioxide equilibrium conditions. However, crop yields and changes in productivity due to climate change will vary considerably across regions and among localities, thus changing the patterns of production. In general, productivity is projected to increase in middle to high latitudes, depending on crop type, growing season, changes in temperature regime, and seasonality of precipitation. However, in the tropics and subtropics, where some crops are near their maximum temperature tolerance and where dryland, non-irrigated agriculture dominates, yields are likely to decrease, especially in Africa and Latin America. Here, decreases in overall agricultural productivity of 30% are projected under doubled carbon dioxide conditions. Therefore, there may be increased risk of hunger in some locations in the tropics and subtropics where many of the world's poorest people live.

Water resources

Currently 1·3 billion people do not have access to adequate supplies of safe water, and 2 billion people do not have access to adequate sanitation. Today, some 19 countries, primarily in the Middle East and Africa, are classified as water-scarce or water-stressed. Even in the absence of climate change, this number is expected to double by 2025, in large part because of increases in demand from economic and population growth. Climate change will further exacerbate the frequency and magnitude of droughts in some places, in particular Africa where droughts are already a recurrent feature. Developing countries are highly vulnerable to climate change because many are located in arid and semi-arid areas.

Sea-level rise

Sea-level rise can have negative impacts on freshwater supplies, fisheries, tourism, exposed infrastructure, agricultural and dry lands, and wetlands. It is currently estimated that about half of the world's population lives in coastal zones, although there is a large variation among countries. Changes in climate will affect coastal systems through sea-level rise and an increase in storm-surge hazards, and possible changes in the frequency and/or intensity of extreme events. Impacts may vary across regions, and societal costs will greatly depend upon the vulnerability of the coastal system and the economic situation of the country. Sea-level rise will increase the vulnerability of coastal populations to flooding. An average of about 46 million people per year currently experience flooding due to storm surges; a 50-cm sea-level rise would increase this number to about 92 million; a 1-m sea-level rise would increase this number to 118 million. The estimates will be substantially higher if one incorporates population growth projections. A number of studies have shown that small islands and deltaic areas are particularly vulnerable to a 1-m sea-level rise. In the absence of mitigation actions (e.g. building sea walls), land losses are projected to range from 1·0% for Egypt, 6% for Netherlands, 17·5% for Bangladesh, to about 80% of the Marshall Islands, displacing tens of millions of people, and in the case of low-lying small island states, the possible loss of whole cultures. Many nations face lost capital value in excess of 10% of GDP. While annual adaptation/protection costs for most of these nations are relatively modest (about 0·1% GDP), average annual costs to many small island states are much higher, several per cent of GDP, assuming adaptation is possible.

Economic costs

A number of policy-makers believe that the cost of mitigating climate change is too high; it might cost 1–2% of gross domestic product. IPCC concluded that there are many technologies, policies and practices that can be used to reduce greenhouse gas emissions without a significant effect on economic growth. Furthermore, it is important to recognize that there are costs of inaction: the IPCC estimated that the social costs of climate change in a doubled-CO2 world could be between 1 and 2·5% of world GDP, and between 5 and 9% of GDP in developing countries. Those estimates are very uncertain, but the basic point is that inaction has social and economic costs.

Actions to protect the environment

The environment must not be considered to be separate from economic development. For example, the issues of climate change and the conservation and sustainable use of biodiversity need to be integrated into all development decisions. There is a need to integrate biodiversity concerns into agriculture, forestry, and coastal zone management, and climate change concerns into energy, forestry and agricultural practices. Sustainable agricultural practices will improve soil carbon, hence soil fertility, and assist in the protection of the climate system by sequestering atmospheric carbon.


Both in-situ and ex-situ techniques can be used to protect biodiversity. However, while in-situ conservation is clearly the preferred technique, complemented by ex-situ techniques, the challenge of using protected areas is potentially complicated if the projected human-induced changes in climate were to occur. As noted earlier, if the climate were to change as projected by the IPCC, biome boundaries could move 150–650 km polewards and 150–650 m upwards in altitude. So, if we are going to use or rely on protected area systems to protect biodiversity, we need to think very carefully about how ecological/biological corridors can be used in order to assist species to migrate. In addition, it is clear that the scale of conservation has to change. It is no longer adequate to think about protecting small areas, but an ecosystem/landscape approach is needed. For example, a study is in progress in the States of Oregon and Washington in the USA, which is examining ways to join the current wilderness areas and the national forests into one conservation area. However, the key challenge is not just to increase the number of protected or conservation areas, but to understand the structure and functioning of ecological systems so that they can be used in a sustainable manner in order to meet the needs of a growing population, which is increasingly wealthy. One of the goals of the Convention on Biodiversity is the equitable sharing of the benefits that can be derived from biodiversity. This can best be achieved by learning how to create and use markets in an equitable manner.

One of the single most cost-effective approaches to conserving biodiversity is to remove the perverse subsidies that lead to the loss of biodiversity. There is a need to eliminate perverse agricultural and forestry subsidies that lead to unsustainable land-use management practices. Similarly, one of the most effective ways to mitigate climate change is to remove energy and transportation subsidies that result in the inefficient production and use of energy. Worldwide, subsidies for agriculture, fossil fuels, transportation and water amount to hundreds of billions of dollars annually. The fundamental problem is that subsidies drain the national budget, rarely assist those they are designed to assist (normally the poor) and lead to the inefficient use of resources. For example, a critical problem in many countries is that water is viewed as a public good rather than an economic good; hence, there is little incentive to conserve and use it wisely. While it is often said that there is not enough money to conserve biodiversity, the magnitude of the subsidies that are leading to the loss of biodiversity are huge in comparison to the amount of money needed for the conservation and sustainable use of biological diversity.

Climate change

A major event occurred in Kyoto, Japan last week (December 1997). Annex 1 countries (developed countries and countries with economies in transition) agreed to an average 5% decrease in greenhouse gas emissions in 2008–2012 relative to 1990. That is a major step towards protecting the Earth's climate system. It is not as much as many people wanted, especially the environmental NGOs, and it recognized that this step alone will not solve the climate change problem. However, it will send an important signal to industry that there will be a growing market for energy-efficient technologies, both in the production and use of energy. In addition, there will be an ever-increasing market for low- and no-carbon energy production technologies.

The agreement in Kyoto is the first step towards meeting the ultimate goal of the Framework Convention on Climate Change (FCCC), i.e. stabilization of the atmospheric concentration of greenhouse gases at a level that will prevent dangerous anthropogenic perturbation to the climate system (Article 2). Defining ‘dangerous’ is not the job of scientists; it is not a scientific issue. The role of the scientific community is to inform policy-makers of the implications of different policy decisions. Policy-makers have to decide what is ‘dangerous’.

Article 2 of the FCCC states that ‘ecosystems should be able to adapt naturally’. Obviously as all ecologists know, ecosystems do not adapt; species do. While the politicians may not have phrased the goal in precise scientific terms, they explicitly have acknowledged that ecosystems are important. Article 2 also states that ‘food production should not be threatened’. However, they did not state whether food production should be secure at the local, national, regional or global scale. As discussed earlier, global food production may not be threatened by climate change, but there will clearly be significant changes at the local and regional level, with significant reductions in agricultural productivity in Africa and Latin America. Hence, an interesting question is how to operationalize the FCCC goal that food production should not be threatened. A third goal of Article 2 of the FCCC is that economic development should be sustainable – again the scientific community can help policy-makers operationalize that goal through scientific and economic knowledge. Article 2 does not explicitly mention human health, water resources and human settlements, but it is clear that there cannot be sustainable economic development without taking into account health costs, water resource issues and human settlements.

Other key issues where the scientific community can provide valuable information for decision-makers is to quantify the uncertainties in scientific understanding and explain what the implications of these uncertainties are for policy formulation. Another issue is that of the time constants of the climate system. There is a long lag-time between emissions and effects and some of the consequences of climate change are irreversible. Furthermore, there are equity issues. Climate change is a global problem, but most of the increase in greenhouse gas concentrations in the atmosphere are due to emissions from the industrialized countries, both in absolute terms and in per capita terms. In contrast, in 30 years time, most of the emissions will probably come from developing countries. The industrialized countries have caused the problem, but developing countries will suffer most. Eventually, all countries will have to limit their greenhouse gas emissions to achieve stabilization of greenhouse gas concentrations, but in the near-term the industrialized countries must take the lead to reduce their emissions. We must not arrest poverty alleviation by putting the economic burden of reducing greenhouse gas emissions on developing countries. The issue of responsibilities is a major ethical issue. Many in the US Congress appear to believe that there should be similar restrictions on emissions from China and India as for the USA.

There is a wide variation in ‘winners and losers’. For example, agricultural productivity will increase in the USA and Russia, but decrease in Kenya and Botswana. The scientific community can help policy-makers understand the implications of different stabilization levels of greenhouse gas concentrations and different emissions pathways to stabilization. The scientific community can also provide them with technical and economic information to assist them in choosing the most cost-effective technologies, policies and measures to limit greenhouse gas emissions. The choice of adaptation and mitigation techniques will vary from region to region. What will work in one region will not work in another region. There will need to be an adaptive approach to solving all of these problems. Nobody knows what the right levels of stabilization are.

Calculations have been performed to estimate the time profile of global emissions of greenhouse gases that are consistent with different stabilization levels of atmospheric concentrations. To stabilize at 450 parts per million of CO2 (note that the preindustrial level was 280 p.p.m.; today's level is 360 p.p.m.), global emissions would have to be decreased immediately. To stabilize at 550 p.p.m., the long-term goal espoused by the European Union, would mean that global annual emissions could increase to about 9·5 billion tonnes of carbon by 2030, and then decrease to below today's level (about 6 billion tonnes of carbon per year from energy sources) over the next 100 years. But in all instances, whether the stabilization goal is 350 p.p.m. or 750 p.p.m., global emissions will have to be significantly less than projected for business as usual in the near term. Hence, there must be significant changes in energy technologies and practices; otherwise, there will be major impacts on human health, managed and unmanaged ecological systems and socio-economic sectors, especially water and agriculture.

Political vs. environmental spatial scales and time-frames

Two of the basic problems associated with these global environmental issues are the large spatial scales and long time scales. Our immediate human interest is often local and as short as days to months, similar to the spatial and time scales associated with weather. However, the spatial and time scales associated with natural and human-induced changes in climate and biodiversity range up to the global scale and from decades to centuries to millenia. The political process is the election period, often 2–6 years, and local (e.g. in the USA it is the Congressional district, State or Country). Therefore, the temporal and spatial scales of importance to many politicians are very different to scales associated with evolutionary processes and climate change. A major challenge is to get politicians to take action on environmental issues, such as climate change and loss of biological diversity, for which they cannot see the damage today, there are scientific uncertainties, the economic costs of action are perceived to be large, there is a vested interest of some important stakeholders in maintaining the status quo, and the decisions they make today will primarily have their effects long after they are out of office.

The World Bank

Lastly, let me briefly address the role of the World Bank, which recognizes that local environmental issues of water and air pollution, in conjunction with global environmental issues pose a major threat to sustainable development.

The World Bank is working with client countries to mainstream the environment into all sectors, e.g. biodiversity into agriculture, and climate into energy. We are trying to transform the marketplace to be ‘greener’, i.e. we are working with environmental groups and industry to promote green consumerism and to promote the incorporation of loss of natural capital and environmental degradation in the calculation of national accounts. We recognize that there is a need to increase the financing available to deal with global environmental issues and that Official Development Assistance (ODA) alone will not solve environmental problems in developing countries. Therefore, the Bank has started work on creating markets for global public goods, such as carbon. There is no doubt that our clients are taking biodiversity much more seriously. In 1988 there was almost no lending for biodiversity; today the Bank has a portfolio of 1·5 billion dollars. Some of it is concessional funding (funds from the Global Environmental Facility), but the remainder are regular Bank loans, which means that clients have to repay the loan.

The Bank recognizes, like most biodiversity specialists, that the most threatened ecological systems are largely in the tropics. The Bank is working with Conservation International to evaluate whether a ‘Critical Ecosystems Partnership Fund’ can be established to help protect about 24 of the most threatened ecosystems around the world. Furthermore, the Bank recognizes that while governements are debating whether there should be a forest convention or not, the world's frontier forests are being destroyed at a rapid rate. Therefore, the World Bank is forming a partnership with the WWF. Over the next 5 years the partnership, working closely with governments around the world, is committed to establish 50 million hectares of new protected parks (forests) and to convert an additional 50 million hectares of ‘paper’ parks (forests) into real protected areas. In addition, the Bank believes that very little forestry at present is truly sustainable. Therefore, the World Bank–WWF Alliance is committed to bringing 200 million ha of the world's forests (100 Mha in the tropics and 100 Mha in temperate and boreal systems) into a sustainably managed system with third party certification.


In conclusion, the scientific community needs to integrate the natural sciences with the socio-economic sciences, take a more multi- and interdisciplinary approach and deal with environmental issues in a more holistic manner. As scientists, we need to learn to talk more effectively to governments and the media so that the public can understand the relationship between their activities, the environment and sustainable development.


  1. * The text of the Sixth BES Lecture delivered on 16 December 1997 at the University of Warwick during the Winter and Annual General Meeting.