The high likelihood of extinction of many plant species that make up Earth's most familiar landscapes by the end of the century, Reuters reported. According to a major study in the journal Science, as the climate crisis increases, it is explicitly growing to be a main reason behind species loss because of the radical shortening and reshaping of geographical regions appropriate for plant survival. 

An international research team developed a model to predict the geographic distribution of 67,000-plus vascular plants: the majority of the world's species with specialized water and nutrient carrying tissue (~18%) By looking at location records for millions of species together with projections of greenhouse-gas emissions levels (constructed for the years 2081 to 2100), the scientists came to a depressing conclusion: between 7% and 16% of these species would lose >90% of their current habitat, making them extremely vulnerable to extinction. 

The threatened plants include the Catalina ironwood, a rare California native tree found only on the Channel Islands, and blue spike-moss, one of the most ancient species on the planet, believed to have evolved over 400 million years. Around one third of all Eucalyptus species are also at risk from the crisis, and they are one of Australia's most iconic and ecologically important plant families. 

The researchers analyzed these changes by applying the idea of a "climate envelope," which is the range of known temperature, precipitation, soil moisture, other physical conditions, landscape characteristics (such as shade) and other variables that are important for a species' growth and survival. In warmer-than-normal climates, these envelopes change shape, which prompts plants to alter their locations over generations using wind, water, gravity and animals to carry their seeds and spores. 

That is just part of the problem, though, with temperature. In many parts of the world, these ecological parameters are being shrunk and squeezed together by climate change, thus reducing the number of regions where all ecological conditions are met for survival. To assess the potential for conservation strategies, the migration rates of realistic plants and the idealised plants were compared, in which plants migrate across the landscape at the same time as a generation of plants moving as a whole group. Interestingly, the extrapolated extinction rates were almost the same for both scenarios. The discovery has serious implications for international conservation policy. But if migration is the main problem, then assisted migration (actively moving plant and animal species to suitable new locations) may be a viable solution to abate the crisis. However, with the overall loss of habitat due to climate change, it will most likely not be enough to simply assist species in moving. 

Environmental damage is predicted to diAer widely across regions. Extreme polar climates are diminishing, and cold adapted vegetation is contracting to extremes. Other areas, such as those with dry climate conditions (American West and Mediterranean climate) are at increased risk due to increased droughts, diminished soil moisture and increased wildfires. In contrast, physical boundaries to migration are present in southern and eastern coastal Australia that prevent movement towards the poles to cooler climates in response to increasing heat. 

At the same time, the researchers predict a process that they refer to as "global reshuAling. Scattered around about 28 per cent of the land surface, the Earth can only have more diversity locally, especially in the tropical and subtropical reaches of the planet, where increased precipitation would create new habitat for those that live on the planet's surface. 

The authors warn, though, that the localised successes are no signal of plants doing well on global scales. Rather, these migrations will create "novel communities," communities of plant species that are new in space because they have never interchanged evolutionary histories before. Researchers acknowledge they can currently do no more than speculate on how these new relationships in the ecosystem will develop or if these communities will succeed. 

Plants form the basis of nearly all terrestrial ecosystems, containing almost 90% of the carbon on Earth, contributing to topsoil stability, supporting wildlife, and supplying both food and medicine for humans and materials for industry and economy, so their loss will have catastrophic cascading eAects. An above-ground dangerous vicious circle may develop: reduction in the global vegetation cover because of climate change would cause uptake of the atmospheric CO2 to turn slower, thus worsening global warming and increasing further die-oAs of vegetation. Finally, the conservation of biodiversity of plants, landscapes and spreading cultures is no simple issue of nature conservation but an essential aspect of maintaining the bottom tier of ecological services that enable human societies.