Professor Iain Colin Prentice, Chair in Biosphere and Climate Impacts reports back on his session at the Our Common Future conference in Paris
This was a lively session, dealing with quite a controversial topic. It had been formed of two proposed sessions, one led by the Grantham Institute (with Georgina Mace, UCL), the other led by Sandra Lavorel, CNRS for the Transformative Adaptation Research Alliance.
I started by putting the record straight about the rates and velocities of climate change and biotic impacts as represented in recent publications, including the IPCC Working Groups I and II reports. I noted that the WG I chapter on past climates had expressed the rates of natural climate change at the end of the last ice age, first in degrees per ten thousand years, and then in degrees per thousand years. This was a perverse choice, as the final transition actually took place in a few decades, as is well established, and indeed carefully reported in the chapter’s main text. The widespread belief that currently projected 21st century climate change is unprecedented in magnitude and rate (shown in statements that horizontal velocities of climate change will soon vastly exceed species’ migration abilities) is thus not supported by evidence. The problem was compounded in WG II, where it was reported that large mammals face the lowest (and trees the highest) obstacles to migration in a changing climate. Yet large mammals have repeatedly suffered the most, and trees the fewest, extinctions after large and rapid warming events.
Evidence from the past
Georgina Mace continued by drawing out how conservation policy might be misled by the neglect of evidence from the past. In response to large and rapid climate changes, some species of animals and plants just stay put (toleration); some shift habitats, but not ranges; some migrate (sometimes over thousands of km); a few become extinct. This doesn’t square with the ruling narrative of mass extinctions due to climate change. It draws attention away from what is and likely will continue to be the major cause of anthropogenic extinctions, namely the fragmentation and loss of habitats. Georgina pointed out that conservation policy needs to be pragmatic rather than apocalyptic, and to recognize the limits to prediction, given the limits of our process-based knowledge of the controls on plant and animal distribution today. We should not abandon the goals of conservation as currently practised, except that focus needs to shift from species conservation in situ towards the facilitation of natural adaptation by ecosystems and the maintenance and enhancement of the services they provide.
Subsequent speakers focused on adaptation, and the futility of top-down approaches that ignore the fact that people will have to adapt. It also arose repeatedly that we are not well adapted to the climate we have – otherwise the economic and human losses from tropical storms, for examples, would not be as great as they still are – and that if we were well adapted to present climate we would also be more resilient to a changing climate.
A large panel assembled for the final discussion. Among the points discussed was the question of who produces the synthetic knowledge contained in IPCC reports. A notable and yet only recently remarked-on feature of IPCC is that its lead author teams in general do not include practitioners, such as conservationists. It has been said with truth that IPCC is “written by scientists, for scientists”. Scientists determine what questions IPCC addresses. (IPBES allows a limited degree of stakeholder involvement; it remains to be seen how effective this is.) However, the questions asked by scientists are likely to be the questions that happen to be topical in one or another branch of science. They are not necessarily the ones that need answering.
Read our briefing paper on Climate change and challenges for conservation by Colin Prentice and Georgina Mace