Some of the plants that make familiar landscapes recognizable may not survive by century's end as climate change becomes an increasingly important driver of species loss, according to scientists, reshaping and often shrinking suitable habitats that the plants need to survive.
Researchers modelled future ranges for numerous species of vascular plants, a category that accounts for almost all the world's plants - those with water- and nutrient-carrying tissues. They looked at more than 67,000 species, meaning about 18% of the world's known vascular plants.
They found that 7% to 16% could lose more than 90% of their range, placing them at high risk of extinction. Examples include Catalina ironwood, or island ironwood, a rare endemic California tree, bluish spike-moss from a plant lineage dating back more than 400 million years, and roughly one third of Eucalyptus species, one of Australia's most recognizable plant groups.
The researchers came to their estimates after examining millions of records on plant locations as well as greenhouse-gas emissions scenarios for 2081-2100.
A plant's habitat is not simply a place on a map, but the full array of conditions it needs: temperature, rainfall, soils, land use and landscape features such as shade.
"One way to picture this is to imagine plants trying to follow a moving 'climate envelope.' As temperatures warm, many species can shift northward or uphill to stay cool enough. But temperature is only part of the story," Junna Wang, a Yale University postdoctoral researcher, and Xiaoli Dong, a professor of environmental science and policy at the University of California, Davis, said in joint comments to Reuters. Wang and Dong helped lead the study published in the journal Science.
In many places, the study indicated, climate change is shrinking these combinations, leaving fewer areas where all the conditions that a species needs still exist together.
For plants, movement, or dispersal, usually happens across generations, via seeds or spores carried by wind, water, animals or gravity. Yet when the researchers compared realistic movement with a scenario in which plants could reach any newly suitable habitat, extinction rates were very similar.
"If slow movement were the main problem, then allowing unlimited dispersal should dramatically reduce extinction risk. But that is not what we found," Wang and Dong said.
That matters for conservation.
"If dispersal limitation were the main driver, then strategies like assisted migration - physically helping species move to new areas - could solve much of the problem. But if climate change is reducing the amount of suitable habitat overall, then simply helping species move may not be enough," they added.
The projected impacts vary by region. Cold-adapted plants in the Arctic may lose habitat as extreme cold climates shrink. Dry regions, including parts of the western United States and Mediterranean-climate regions, face risk from stronger drought, lower soil moisture and more frequent wildfires. In southern and eastern coastal Australia, coastlines may limit poleward shifts.
At the same time, local plant diversity could rise across about 28% of Earth's land surface as species move into newly suitable areas, including parts of the tropics and subtropics where increased rainfall - rather than temperature alone - could make conditions suitable for additional species, the researchers found.
They described this as a global reshuffling, with some species disappearing from parts of their historical range while others move into new areas, but said local gains do not mean plants are doing better overall.
These shifts could also create "novel communities" - combinations of plants that have not historically lived together but would begin encountering one another for the first time. How would these interactions play out? The researchers said they do not know.
Plants underpin most terrestrial ecosystems. They store carbon, stabilize soils, support wildlife and provide food, timber, medicines and other materials. So changes in plant diversity can have cascading effects on nature and people.
"If climate change reduces vegetation cover, ecosystems may absorb less carbon dioxide from the atmosphere, which can further intensify warming. That creates a feedback loop in which climate change harms plants, and reduced plant cover/productivity in turn worsens climate change," Wang and Dong said.
"Ultimately, protecting plant diversity is not only about conserving nature for its own sake - it is also about maintaining the ecological systems that support human societies," they said.
