Climate Change and the Variety of Life
Climate is a condition of life; and life is perhaps the most amazing thing about the universe and our tiny world within it. Life has been well called the biospheric membrane wrapped around the Earth. Its surface is wafer thin. E. O. Wilson once wrote of a hypothetical journey outwards from the centre of the Earth.
"For the first twelve weeks you travel through furnace-hot rock and magma devoid of life. Three minutes to the surface, five hundred meters to go, you encounter the first organisms, bacteria feeding on nutrients that have filtered into the deep water-bearing strata. You breach the surface and for ten seconds glimpse a dazzling burst of life, tens of thousands of species of micro-organisms, plants and animals within a horizontal line of sight. Half a minute later almost all are gone. Two hours later only the faintest traces remain consisting largely of people in airliners who are filled in turn with bacteria."
That wafer-thin repository of life is contained within the atmosphere, itself a turbulent highly reactive chemical mixture of gases we call climate. Yet the turbulence of the climate has a stability of its own. Over the long history of the Earth, climate has been influenced by a bewildering complexity of factors.
From outside the Earth system, solar radiation has gradually increased. How it falls on the Earth's surface is subject to variations in the Earth's orbit, its tilt and the way it spins. Then there have been hits from space. Perhaps the most devastating was 250 million years ago when the effects caused the extinction of some 90% of marine species. More notorious was the bolide of 65 million years ago which so changed atmospheric conditions that it ended the long dominance of the dinosaur family.
From inside the Earth system the slow movement of tectonic plates profoundly affects climate. Land masses crash and separate. Mountains rise and fall. Sometimes volcanic dust shrouds the Earth. Ocean currents take new tracks. Throughout living organisms have adapted themselves to new circumstances while helping to create them.
Once life had started it began to evolve, and the atmosphere with it. By preserving and making use of water, carbon, hydrogen and sunlight, living cells transformed their physical surroundings and the rocks, muds and gases of which they were composed. Its detritus is under our feet. Photosynthesis and oxygenation are the two driving forces which have made the world we know.
The complexity of life, now and in the past, is beyond measurement. As it has evolved over hundreds of millions of years, its proliferating parts have remained interconnected, and in different degrees interdependent. Obviously living organisms find some physical circumstances more comfortable than others, and take advantage of them. Less obviously, living organisms through the familiar mechanisms of natural selection, genetic mutation, symbiosis and chance are able within limits to establish the physical circumstances which best suit them.
Neither climate nor life will continue indefinitely. Eventually our Sun will become a red giant, and expand to near the orbit of the Earth. Long before then life on Earth will be extinct.
My theme tonight is the relationship between climate change and the diversity of life but our understanding of both is far from complete. During the last ten million years, gradual cooling led to the succession of Pleistocene ice ages, interspersed with warm interglacials, which transformed living conditions all over the Earth. The processes of evolution sometimes quickened, and sometimes slowed down. Even 100,000 years ago the biospheric membrane was very different from what it is today. The present interglacial began about 10,000 years ago, with wobbles between warming and cooling since then. But even in this relatively short and stable patch of geological time, great changes have taken place.
The handiwork of one animal species - our own - has become increasingly evident. From North America to Australia, humans hunted down the big mammals, and the transition from hunter gathering to settled agriculture, with steep increases in human numbers, led to deforestation on a vast scale, with resulting variations in local climate. The growth of cities accelerated all such changes; and the industrial revolution, which began around 250 years ago, accelerated them still more.
It is notoriously difficult to distinguish natural from human-made changes in climate, and to determine if and when human activity became decisive on more than a local scale. During the last thousand years, there were clear natural changes. Warming in the early Middle Ages allowed farming in Greenland and wine-growing in southern England. There were droughts in Western Europe in the 13th century; increasing cold, leading to economic recession linked to the Black Death, in the 14th century; ice fairs on the River Thames in the 17th century; and warming in the northern hemisphere from around 1880, rising steeply from the 1970s onwards.
Successive reports from the Intergovernmental Panel on Climate Change, which brings together the vast majority of the world's experts on the subject, show that the human contribution to climate change is now having a significant if not decisive effect. Indeed in its most recent guidance to policy makers in 2001, the scientific working group of the Intergovernmental Panel concluded that
"... in the light of new evidence and taking into account the remaining uncertainties, most of the observed warming over the last 50 years is likely to have been due to the [human-induced] increase in greenhouse gas concentrations".
How warm would a warmer world be? According to the same group, "the globally averaged surface temperature is projected to increase by 1.40 ēC to 5.80 ēC over the period 1990 to 2100". This is a considerable increase on the 1.00 ēC to 3.50 ēC rise suggested in its previous report of November 1995. It covers a wide range of local variations. But overall,
"the projected rate of warming is much larger than the observed changes during the 20th century, and is very likely to be without precedent during at least the last ten thousand years ..."
Uncertainties remain. What is certain is that average world surface temperature is rising; six of the hottest years of the 20th century occurred during the last decade. Although confidence in the modelling has increased, there remain many uncertainties which make it difficult to quantify the risks involved, or the regions most likely to be affected.
What would a warmer world look like? Here the uncertainties, region by region, multiply. Efforts have been made by the Intergovernmental Panel to assess possible impacts by continent, but the results are inevitably sketchy. However interpreted, they suggest a different world and a correspondingly different distribution of human activity as people and other living organisms adapt to change. Such change includes new patterns of rainfall and drought, more extreme events, and rising sea levels. For many it could be, as was well said, a genuine weapon of mass destruction.
First there are impacts on vegetation. We are already seeing tropical forest die back in northern Brazil, thereby adding to the deforestation in Amazonia caused by human agency. Recent reports suggest an area the size of Wales was deforested last year alone. There could be repercussive effects on hydrology throughout the Amazon basis eventually reaching as far north as Arizona. The transformation of tropical grasslands to desert or temperate grassland is increasing in Africa.
Next there are impacts on water resources, and in particular increased stresses in countries, particularly in Africa, subject to annual variations in rainfall.
Food supply is obviously affected. There may be increased crop yields in high and mid-latitude countries, but decreased yields in lower latitudes. In Africa there could be many more people at risk of hunger due to climate change alone by the 2050s. Already Africa is dependent on food imports to feed itself, and becoming more so.
Other impacts of climate change will be on coastal communities. Global sea level rise is a major hazard with incalculable consequences. It is also poorly understood. Recent work on the Arctic and Antarctic polar ice sheets shows that if temperature increases by more than about 30 ēC, cumulative melting could take place, and sea levels world wide could rise by many metres. At present the Intergovernmental Panel forecast is a rise of between 19 to 88 cms by 2100. Anything like the higher figure would put tens of millions of people at risk.
Human health will be affected. Micro-organisms respond rapidly to changes in temperature and moisture. Humans take 20 years to reproduce. Bacteria do the job in 20 minutes. Old diseases such as malaria could return and new diseases could arise, and have already done so.
Then there are the two jokers in the pack. There is the possibility of weakening of the Atlantic conveyor, which could bring renewed glaciation to Western Europe and eventually elsewhere as during the Younger Dryas 12,000 years ago. On the other hand there is the possibility of a runaway greenhouse effect, as at earlier times in the Earth's history, such as possibly at the Permian / Triassic boundary 250 million years ago, and at the Palaeocene / Eocene boundary 55 million years ago. In each case vast releases of methane may have been the cause.
In Britain the Government has made more detailed predictions under its Climate Impacts Programme. It has recently produced its second set of scenarios of future impacts here. First our climate is likely to become warmer. By the 2080s the average annual temperature may rise by between 20 ēC and 3.50 ēC. There will be greater warming in the south and east rather than in the north and west, and there may be greater warming in summer and autumn than in winter and spring. High summer temperatures will become more frequent, whilst very cold winters will become more rare.
A very hot August, such as experienced in l995 when temperatures over England and Wales averaged 3.40 ēC above normal, may occur one year in five by the 2050s and as often as three years in five by the 2080s. We had a painfully hot August last year. At the same time winters are likely to become wetter and summers drier throughout Britain. In the south and east summer precipitation may decrease by 50% or more by the 2080s and winter precipitation may increase by up to 30%.
Round our shores sea level will continue to rise. This may be the most serious change of all. The problem is confounded by another factor: that of isostatic change. Since the last ice age much of southern and eastern Britain has been sinking, and northern and western Britain have been rising in relation to sea level. The map of British coastlines will look very different by the 2080s.
A good illustration of human vulnerability to climatic change world wide lies in the effects of the Niņo (otherwise known as the El Niņo Southern Oscillation or ENSO), or its opposite the Niņa. Relatively small changes can have gigantic effects. As most people now know, the Niņo signifies the arrival every four to six years or so of warm water from the western Pacific which overlies an upwelling current of cool water from the south. It thereby changes weather conditions, first within the region and then in different degrees in other parts of the world. Around a quarter of the Earth's surface is affected by it one way or another.
During a Niņo year there are severe droughts in the countries bordering the western Pacific: Indonesia, New Guinea, north-east Australia and the Philippines, with weakened summer monsoon rainfall over southern Asia generally, including India. In the countries bordering the eastern Pacific it is the reverse: there is heavy rainfall in northern Peru, Ecuador and Chile with drier spots in southern Peru and Bolivia.
Further away concurrent changes have been observed. For example north-east South America and southern Africa are drier, and east Africa and the southern United States are wetter. There tend to be fewer Atlantic hurricanes: the reason is that westerly winds in the upper atmosphere blow the tops off hurricane formations before they have time to gather strength. In Niņa years it is the opposite with more Atlantic but fewer Pacific hurricanes (otherwise known as typhoons).
Such perturbations obviously affect the conditions of life in all its aspects. For some organisms - from plants and insects to fish and mammals - it is a disaster, with sharp falls in population density; for others it is an opportunity to be exploited while it lasts; but for most it must be an experience which they are broadly adapted to cope with, or at least to recover from.
Micro-organisms deserve a special word. Floods bring opportunities for the vectors of such diseases as malaria, dengue and yellow fever, encephalitis and schistosomiasis, and for the agents of such diseases as hepatitis, dysentery, typhoid and cholera. Recent research has suggested mechanisms for the spread of cholera in South America during Niņo events. Warm or brackish water combines with run off from the land to produce local plankton blooms in which the cholera bacillus flourishes.
Another example is the apparent relationship between the Niņo and epidemics of African horse sickness. No doubt there are comparable stories to tell about other parts of the world.
Not surprisingly the scale of the changes symbolized by the Niņo, with prospects of more to come, has brought together the world's scientific community in unprecedented fashion. Let me refer you to a Declaration made by over a thousand scientists from the four great global research programmes at Amsterdam in July 2001. There it states squarely that
- Human-driven changes to the Earth's land surface, oceans, coasts, atmosphere and biodiversity are "equal to some of the great forces of nature in their extent and impact Global change is real and happening now".
- "Human activities have the potential to switch the Earth's System to alternative modes of operation that may prove irreversible and less hospitable to humans and other life ... the Earth's System has moved well outside the range of the natural variability exhibited over the last half million years at least ... the Earth is currently operating in a no-analogue state."
- "The accelerating human transformation of the Earth's environment is not sustainable. Therefore the business-as-usual way of dealing with the Earth's System is not an option. It has to be replaced - as soon as possible - by deliberate strategies of management that sustain the Earth's environment while meeting social and economic development objectives."
The same themes have been taken up by others since then. On 14 November last year Science ran a series of articles on our planetary prospects, underlining the effects of damage to the global ecosystem.
On biodiversity Martin Jenkins wrote that nearly half the Earth's land surface had been transformed by direct human action and that the indirect efforts were beyond calculation. The result with big regional variations was almost bound to be conversion of more land to crops, with increasing loss of forests and natural habitats, and degradation of land, particularly in tropical countries. This meant continued, even accelerating, loss of natural ecosystems, and their replacement by "less diverse, often intensively managed systems of non-native species". We could not
"continue to manipulate or abuse the biosphere indefinitely. At some point some threshold may be crossed, with unforeseeable but probably catastrophic consequences for humans."
On climate, the Government's Chief Scientific Adviser wrote a forthright article, also in Science, on 5 January 2004, when he said that delay in tackling the specific issue of climate change "for decades, or even just years" was "not a serious option", and it represented
"the most severe problem we are facing today - more serious even than the threat of terrorism."
This is strong stuff. It conforms with the depressing conclusion in the Global Environmental Outlook 2000 report of the UN Environment Programme that almost all environmental problems are getting worse and in many cases the long-term effects have yet to be seen. An additional factor is the widening gap between the world's rich and poor people, and the disproportionate consumption of the Earth's resources.
So what on Earth - a familiar phrase - are we going to do next? The problems are so intimidating that most people, including politicians and leaders of all kinds, simply do not want to confront them, or feel capable of doing so. The bridge between science and politics is always long and rickety.
There have been many conferences, some international agreements like those on climate change and protection of biological diversity, and three world summits (Stockholm 1972, Rio de Janeiro 1992, and Johannesburg 2002). But even if some governments, including our own, have begun to take action on some of the issues, for example energy and transport policy, most have continued to ride a tide which carries them ever further in the wrong direction. The biggest villain is the biggest polluter.
The Bush Administration in the United States seems wilfully determined to pretend that the problems are unproven, and to ignore the advice of its own as well as of the world's scientists. Even those who accept the premise of the need for change have very different priorities. It is easy to bleat about the problems but more difficult to set priorities for action. My own are as follows:
- We need urgent action on climate change. So much has been said on this that I will not repeat it. Let me say simply that I do not think that technical wheezes - mirrors in space, windmill extractors, iron sprays in the oceans, cloud whitening and the rest - could ever do the trick, and would probably create more problems than they solved.
- We need new thinking and policies on protection of biodiversity within conservation generally. Hence the importance of the Millenium Ecosystem Assessment due to report next year, and, in the next ten years, the Tree of Life project to demonstrate relationships between organisms by descent. I shall have a word or two to say about this in a moment.
- We need to look again at economics and the way we measure wealth, welfare and the human condition in terms of the Earth's good health. Neither state-directed economics nor market economics can alone supply the right framework.
- We need to apply the principles of common but differentiated responsibility, accepting that industrial countries have much bigger responsibilities for what has gone wrong as well as what has gone right, and should give the example in their domestic policies.
- We need to focus on the needs and attitudes of coming generations: in short give new direction to the educational process. This process in industrial, as in any other kind of country, is rightly called capacity building.
All involve the ability to accept accelerating change, learn to think, and ultimately to behave differently.
From my personal experience, it is relatively simple - at least today - to make the case on climate change. The case for conservation is much more difficult. I want to conclude this talk by looking at the four main factors - ethical, aesthetic, economic and ecological - which should drive our thinking, and enable us to make the case to others.
On ethical grounds it is questionable whether we have the right, however defined, to exterminate so many other species on the living planet whether they are of use to us or not. This is not a point which caused Christianity much concern in the past. There are honourable exceptions; but most Christian thinkers have seen humans as separate from the rest of nature which they believe was for their plunder or pleasure.
But respect for life as such has always been a central tenet of Buddhism and Taoism, among other systems of belief. There is an increasing awareness that humans have some kind of ethical responsibility for the welfare, or at least the continued existence, of our only known living companions in the universe.
The aesthetic aspects of nature usually go without saying, but they are equally difficult to define. There is, I believe, a profound human instinct which causes people to feel linked to the natural world. Even the most hardened city dwellers need space and greenery in their work and play. The culture of every people is closely allied to its landscapes and their living inhabitants, and cannot be dissociated from them.
Ethical and aesthetic arguments are of enormous, indeed primal, importance for the psychological health of any society, but they are usually unpersuasive against short-term arguments of self interest. Our economic interest in biodiversity is obvious. We need to maintain our own good health as well as that of the plants and animals, big and small, on which we depend for food. We have our place in the food chain like any other creature, and are more vulnerable than most as predators at the top of it.
As for the ecological factor, we enjoy at present, mostly without recognizing it, an enormous wealth of free natural services. Such services mean a broadly regular climatic system with ecosystems, terrestrial, marine and atmospheric, to match. We rely on forests and vegetation to produce soil, to hold it together and to regulate water supplies by preserving catchment basins, recharging groundwater and buffering extreme conditions. We rely upon soils to be fertile and to absorb and break down pollutants. We rely on coral reefs and mangrove forests as spawning grounds for fish and wetlands, and on deltas as shock absorbers for floods.
Likewise we rely on the natural processes of recycling and waste disposal. We rely upon the current balance of insects, bacteria and viruses; and we assume the health of plants and animals unless we find to the contrary. Yet few realize the extent to which we have been appropriating the resources of the Earth for our own purposes. Already we use - or abuse - some 40% of total photosynthetic production on land. Nature has an importance far beyond that of a warehouse of marketable raw materials.
It is obvious that our current system of values is in urgent need of repair. This will not be a patch-and-mend job, but something more fundamental. A good beginning is to look anew at the apparently humble issue of costs.
Because of our current preoccupation with material wealth and prosperity, many, usually with the best intentions, want to find means of attaching monetary value to almost everything. A variety of methodologies, all limited in scope and some more sensible than others, have been devised for this purpose. Of course some rule-of-thumb method of assessing and comparing values would indeed be useful, not least in giving comfort to economists and more plausibility to their models. Somehow we have to bring in the factor of environmental cost.
Let me quote two good sayings:
- first, the economy is a wholly-owned subsidiary of the environment;
- secondly, markets are superb at setting prices but incapable of recognizing costs.
The problem is how to enlarge understanding of the huge range of issues I have touched on this evening. Perhaps we need a catastrophe, not too big and not too small, not too quick and not too slow. So far there have been few catastrophes with sufficient impact. No-one likes the spread of African bees, the world-wide decline in amphibians, the mass deaths of trees, the eruption of such new diseases as AIDS and of lethal bacteria resistant to antibiotics. The miners' canaries may be dying all over the place but we do not always know why. Nor do we want a hit from space or internal social collapse.
But the price of sticking to our present system of values and not adapting to new ones is intolerably high. So far all past urban civilizations - some 30 of them - have crashed. None over time learned how to reach a well-regulated steady state with population in balance with natural resources. There is no reason to believe that ours is any different. Indeed current signs are to the contrary.
We continue to talk about conquering Nature as if we were not a small but immodest part of it. I end as I began with sheer wonder at the miracle of life, and the sense of human littleness within the tissue of living things. The mediaeval abbess Hildegard of Bingen once wrote:
"... I ignite the beauty of the plains,
I sparkle the waters,
I burn in the sun, and the moon and the stars
I adorn all the earth,
I am the breeze that nurtures all things great
I am the rain coming from the dew
That causes the grasses to laugh with the joy of life."
I think that in all of us there is a most precious impulse: to laugh with the joy of life. The day we no longer do so we are lost indeed.
