No matter how fast a species under threat can move, escape can only be successful if the new destination can meet its needs.
An ecological modeling study from the University of California, Davis, found that 7% to 16% of global plant species studied are expected to lose more than 90% of their range, facing high risk of extinction by 2100 under current climate change projections.
The study, published today in the journal Science, said habitat loss due to climate change is expected to drive these extinctions, not a plant's ability to shift locations or "keep pace" with the changing climate.
This suggests that conservation strategies focused on assisted migration, where people facilitate species range shifts, may not reduce global plant extinctions induced by climate change. However, combining such efforts with restoration and protecting climate change refugia may be more effective.
"We found that what causes extinction is not that plants aren't moving fast enough," said senior author Xiaoli Dong, an associate professor with the UC Davis Department of Environmental Science and Policy. "It is that a large amount of suitable habitat by the end of the century is going to be gone. If our priority is reducing the extinction rate of plant species, aggressively cutting our emissions will be much more important than other actions."
Plants on the move
The researchers wanted to understand how plants are going to respond to warming over the next few decades. Where will they go? How many will go extinct, and what drives that extinction? To answer those questions, they leveraged a large database of nearly 68,000 plant species, which make up 18% of the world's flora. They projected the distributions of these plants through 2100 and accounted for uncertainties, arriving at an extinction rate of 7% to 16% across emissions scenarios.
Most previous models projecting extinction rates do not incorporate the speed of range shifts - how fast species can actually move as the climate changes. This addition showed that habitat loss, not range shifts, drives extinction rates under climate change.
High extinction rates are projected in southern Europe, the western United States and southern Australia, posing risks to both ancient and economically vital plant species. Among them are spikemoss (Selaginella) in California - one of the oldest surviving lineages of vascular plants, dating back over 400 million years - and eucalyptus in Australia, a genus that covers three-quarters of the continent's native forests and is crucial to biodiversity, Indigenous culture and the timber industry.
