This report provides, for the first time, a baseline assessment of our current knowledge on the diversity of plants on earth, the global threats these plants currently face, and the policies in place and their effectiveness in dealing with these threats.
On the diversity of plants, we can report that there are now an estimated ~391,000 vascular plants known to science of which 369,000 are flowering plants. Around 2000 new vascular plant species are described each year. In 2015 these included a massive leguminous tree (Gilbertiodendron maximum), more than 90 species of Begonia, 13 new species from the onion family, and discovery of a close relative of sweet potato (Ipomoea batatas). Most were found during fieldwork, some in herbarium specimens, while one of the largest carnivorous plants known (1.5m in height) a new insect-eating plant, Drosera magnifica was first discovered on Facebook. However, there are still large parts of the world where very little is known about the plants. Identification of these important plant areas is now critical. Similarly, we still only know a fraction of the genetic diversity of plants and whole-genome sequences are currently available for just 139 species of vascular plants.
Knowledge of the impacts of climate change on plants is known for some regions of the world, but there are still large areas for which little or no research exists. In those areas where good data is available, clear impacts are visible including changes in flowering times, turnover in plant communities and movement of species with changing climates.
All but one of the world’s biomes have experienced more than 10% change in land-cover type in the past decade due to the combined impacts of land-use and climate change.
A large global movement of alien invasive plant species is occurring. Around 5000 species are now documented as invasive in global surveys. These plants are causing large declines in native plants, damaging natural ecosystems, transforming land-cover and often causing huge economic losses. Those that are most invasive share a similar life-form – which is the ability to die-back during unfavourable seasons and survive as bulbs, rhizomes, tubers, root buds or seeds. Japanese knotweed is a classic example of this life-form which survives underground as a rhizome.
There are many emerging threats also occurring with plant diseases caused by fungal, bacterial and viral pathogens. Research effort into these diseases is skewed towards countries with a wealthier research infrastructure.
Given the threats associated with climate change, land-use change, invasive plants and diseases, best estimates lead us to believe that 21% of the world’s plants are currently threatened with extinction.
International trade in endangered plants is causing additional pressure on wild biodiversity and strict enforcement of international legislation is crucial. Adoption and implementation of policies such as CITES (Convention on Trade in Endangered Species) other international legislative instruments, such as the Nagoya Protocol, already appear to be having some effect at enabling countries to best conserve and utilise the biodiversity they hold.