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Global plant species are threatened by climate change as habitats shrink

Scientists say that climate change is a major factor in the loss of species. It is reshaping habitats and shrinking them, which plants require to survive.

Researchers modeled future ranges of 'numerous' species of vascular plant, a group that includes 'almost all plants in the world - those which have water- and nutrients-carrying tissue. They?looked? at over 67,000 species. This is about 18% the known vascular plant species in the world.

The researchers found that between 7% and 16% of species could lose over 90% of their range. This puts them at a high risk of extinction. Catalina Ironwood or Island Ironwood is a rare California tree that dates back 400 million years. Blueish spike-moss, which comes from a lineage of plants dating back over 400 millions of years, and approximately one third of Eucalyptus, one of Australia’s most recognized plant groups, are also examples.

Researchers came up with their estimates by analyzing millions of records about plant locations and greenhouse-gas emission scenarios for the years 2081-2100.

The habitat of a plant is more than just a location on a map. It includes all the conditions that it requires: soils, temperature, rainfall, land use, and other landscape features like shade.

Imagine plants following a moving "climate envelope". Many species will move northwards or upwards to keep cool as temperatures rise. Temperature is not the only factor, Junna Wang, a Yale University Postdoctoral Researcher, and Xiaoli Dong, a Professor of Environmental Science and Policy at the University of California Davis, stated in a joint statement. Wang and Dong were involved in the study that was published in Science.

Climate change has reduced the number of places where all conditions necessary for a species are still present.

Plants move or disperse via seeds and spores that are carried by animals, wind, water or gravity. Researchers found that extinction rates were similar when they compared realistic movement to a scenario where plants could reach any new suitable habitat.

If slow movement was the main problem then allowing for unlimited dispersal would dramatically reduce the risk of extinction. Wang and Dong stated that this was not the case.

What matters to conservation?

If dispersal limitations were the primary driver, strategies such as assisted migration -- physically helping species to move to new regions -- could solve a lot of the problem. If climate change is reducing habitats, it may not be sufficient to help species migrate.

The projected impacts differ by region. As extreme cold climates decrease, plants adapted to the Arctic could lose their habitat. 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. The coasts of southern and eastern Australia may be able to limit poleward shifts.

Researchers found that local plant diversity can increase across 28% of Earth’s surface as species migrate to newly suitable areas. This includes parts of the tropics and the subtropics, where an increase in rainfall, rather than just temperature, could create conditions for additional species.

The scientists described it as a global reshuffling. Some species are disappearing from their historic range while others have moved into new areas. However, they said that local gains did not mean the plants were doing better in general.

The shifts in climate could also lead to the creation of "novel community" - a grouping of plants who have never lived together before but will now be interacting for the first. What would happen if these interactions took place? Researchers said they did not know.

Most terrestrial ecosystems are supported by plants. Plants are important because they store carbon, stabilize the soil, provide wildlife with food and medicine, and also produce timber. Changes in plant diversity have a cascading effect on both nature and humans.

If climate change reduces the vegetation cover, ecosystems could absorb less CO2 from the air, which may intensify further warming. This creates a negative feedback loop where climate change damages plants and decreased plant cover/productivity worsens the climate change, Wang and Dong explained.

They said that "protecting plant diversity" is about more than just conserving nature. It is about preserving the ecological systems which support human societies.

(source: Reuters)