Thank you for the opportunity to testify on climate change and its effects on wildlife, namely the rest of life on earth or biodiversity. I am Thomas Lovejoy, President of the Heinz Center for Science, Economics and the Environment, a non-partisan no-advocacy environmental policy center that engages business, government, academia and environmental groups in developing environmental policy.
I have been engaged in the topic of this hearing for more than two decades, having produced the first book on the subject with Rob Peters in 1992 and just two years ago a completely new one with Lee Hannah, a copy of which I present here. The distinct difference between the two, and indeed what led to doing a new one, is that today there are well documented and statistically significant examples of nature responding to climate change. Some of these changes involve different timing in the annual cycles such as migration or flowering, others involve changes in where species occur, yet others involve threshold changes in ecosystems, and some involve systemic changes such as the acidification of the oceans. The data have moved from the anecdotal to the statistically significant (1) and they demonstrate unequivocally that nature is on the move. There is by now a global scientific literature on this subject but I will restrict myself here to American science and examples.
Climate change is not new in the history of the earth, but it is new in the history of human civilization and our dependence on the natural world. For the last ten thousand years, the entire human enterprise has been built on the assumption of a stable climate, including the origin of agriculture which in turn made human settlements possible, and our entire recorded history. For that period the patterns of nature and of individual species and organisms have been attuned to the unusual period of stability. Today we can see the first stirrings. The map of geographical growing zones that constitute a bible for gardeners as to what they can or cannot grow, has recently been revised to accurately reflect the climate change that has already taken place. Tree swallows were laying eggs nine days earlier by 1991 in comparison to 1959 (2), In the western United States there is earlier flowering by 2 days per decade for lilacs and 3.8 days per decade for honeysuckle (3). In the mid-Atlantic experimental evidence shows that poison ivy is favored by higher concentrations of the greenhouse gas CO2. One of the best studied butterfly species in the United States, the Edith’s Checkerspot has changed its geographical range generally moving northward and upslope (4).
One of the immediate consequences and a foreshadowing of things to come are mismatches between species and their environment and linked species. For example if one species depends on temperature for cues and the other day length, climate change will change one and not the other. This has been occurring between the checker spot and the flower species on which it depends (5).In the arctic some seabird species which feed on the Arctic cod, a species which lives on the underside of the ice, are no longer able to breed successfully because the ice edge is too far from the land on which they must nest (6).
The important issue before us is not the stirrings we can already document but the changes that further climate change is likely to engender. Here we can turn for glimpses of the future by pairing climate model projections with what we know of how nature responded to natural climate change in the past – such as during the glacial interglacial swings which preceded the stable climate “sweet spot” which has been so favorable to human civilization. We can anticipate multiple and massive mismatching and wrenching changes in the ecosystems on which we depend. It is quite clear from the fossil record that biological communities do not move as units like Birnam Wood in Macbeth, but rather that individual species move individually at different rates and sometimes in different directions as they attempt to track their required conditions. Basically ecosystems will disassemble and the individual species will assemble into novel biological communities: both a nightmare for natural resource managers as well as for the rest of us, as the shuffling of the ecological decks favors opportunistic species such as weeds, pests and diseases.
It is already clear that there will be threshold changes in ecosystems. One clear-cut example has been occurring in the coniferous forest of western Canada and the northwest United States. There, the naturally occurring pine bark beetle – always part of the ecosystem but held largely in check by other species, has had the balance tipped in its favor by a succession of mild winters and elevated summer night time temperatures. There has been massive die off of trees, the red color of which makes the landscape reminiscent of autumn color in New England (7). Even if it were not to spread farther (and there is no obvious biological barrier) it has had a huge impact on the timber industry and all species that live in those forest, as well creating conditions for forest fires of a magnitude we have never seen.
Threshold changes and more gradual linear changes in ecosystems are driven not only by temperature difference but also by change in precipitation patterns. Obviously that will be a problem for freshwater ecosystems already coping with temperature change. In the American southwest there already is a dramatic example of a threshold change driven by a marked drop in precipitation: in northern Arizona drought has caused a complete die off of trees (8).
It is important to note that the oceans and marine organisms are similarly vulnerable to climate change. (The United States has the greatest amount of marine environment of any nation because of its extensive economic zones). Coral reefs prove to be particularly temperature sensitive and experience bleaching events in which the algal partner of the coral animals is ejected turning that Technicolor world into something approaching a black and white movie. Even more disturbing we have only recently learned (9) that the oceans are increasing in acidity because of the additional carbon dioxide in the atmosphere. This is essentially simple high school chemistry: the more CO2 in the atmosphere the more acid the oceans become. They are already 30% more acid (0.1 pH unit). Increasing acidity has profound implications for all organisms that build shells from calcium carbonate from corals to clams to tiny plankton at the base of most food chains. The calcium carbonate equilibrium is pH dependent.
If this is the case with current climate change, there could be profound effects if climate change is allowed beyond that which is already programmed by current levels of greenhouse gas concentrations. All five of the global climate models for example show that with double pre-industrial levels of CO2 the sugar maple will no longer be able to exist in New England. That is not great news for lovers of maple sugar or autumn foliage. It is even worse news for those organisms that depend of the sugar maple as part of the northeastern deciduous forest.
One of the biggest problems plants and animals will face is the highly modified landscape of modern times. In many instances landscapes will represent obstacles to organisms as they attempt to disperse and track their required conditions. In the case of organisms near the tops of mountains or on low islands, there will be nowhere to go but into thin air regardless of whether they are modified by human activity or not. This has already been noted in pika populations on individual mountains in the American west (10) and foreseen for the key deer with sea level rise (11).
If this is the case with current climate change, there could be profound effects if climate change is allowed beyond that which is already programmed by current levels of greenhouse gas concentrations. This has led to a projection of extinctions from climate change (12). I am not here to defend the exact number, but the general point is that it is a large number if climate change is allowed to go on business as usual.
The question then is where is the danger zone in climate change which should be avoided. Where to stop short? All biologists who have looked at the question believe that double pre-industrial CO2 would be disastrous for plants, animals, and ecosystems. There is some consensus among the conservation organizations that 450 parts per million should be the limit. I for one think that is probably too generous, impractical as that may seem with our current level being at 380. Now there is discussion around what is worse for wildlife: to go into the danger zone and then come down to something like 450 or below, or whether that brings dangers in itself.
What is abundantly clear is that the living world on which we depend is far more sensitive than almost anything else to climate change. Life on earth is sending an urgent warning signal that climate change needs to be engaged with – and with an urgency and scale hitherto not contemplated.