Ecological buffers to climate change are weakening

Human-caused climate change is diminishing the ability of forests and other natural systems to slow global warming, hundreds of scientists say in a new report. Without that buffer, society will not have time to adapt.

The scientists are part of the Intergovernmental Panel on Climate Change (IPCC) working group that assesses the impact of climate change on socioeconomic and natural systems. On Feb. 28, the working group released a summary of its latest report, which focuses on the interactions between the climate, ecosystems, and human society.

Human health and well-being and society’s ability to develop in ways that are resilient to climate change are more dependent on natural ecosystems than previously thought, said Camille Parmesan, chair in public understanding of oceans and human health at the University of Plymouth and one of the authors of the report. In addition, the adverse impacts of climate change are more widespread and more severe than predicted in prior IPCC reports, she said at a news briefing.

Scientists are observing the weakening of the biosphere’s ability to absorb the greenhouse gases that humans produce through actions such as the burning of fossil fuels, Parmesan says. For instance, intact old-growth Amazon rainforest and trees in northern North America take in and store CO₂. But in some locations, these ecosystems are starting to turn from net sinks of carbon­—which suck up more CO₂ than they release—into net sources of carbon, she says.

Some natural systems have “hard limits” on how much climate change they can adapt to, Parmesan says. These are “why we’re seeing species going extinct. That’s why we’re seeing the most sensitive ecosystems—the mountaintops, the high Arctic—having massive changes.”

Humans can intervene to boost some ecosystems’ ability to adapt to climate change. For example, Parmesan says, trees can be planted in areas that were clear-cut. With a diversity of species, a replanted forest is more resilient to climate change and better at carbon uptake and storage than an industrial monoculture of trees, she said.

But activists warn that adaptation alone isn’t the solution to climate change.

“We cannot restore enough wetlands, build ever-higher levees, pop up ever-greater numbers of summer cooling stations, or douse every wildfire we see today—let alone address the needs of a future in which we continually neglect the source of those supercharged [natural] disasters,” Nathaniel Keohane, president of the Center for Climate and Energy Solutions, says in a statement.

“The science is clear: we have a quickly narrowing window to rein in climate change by making deep cuts in emissions, investing in adaptation, and advancing climate-resilient development,” Rachel Cleetus, policy director and lead economist for the Union of Concerned Scientists, says in a statement.

Another IPCC working group, which focuses on options to address climate change, is expected to release a report in coming weeks.