A quarter of all carnivorous plant species are threatened with extinction worldwide, according to the latest analyzes. The green survivors can grow on very nutrient-poor, wet soils thanks to their meat-rich diet. But this is increasingly becoming a problem: Man-made influences such as the destruction of habitats, overfertilization and climate change are causing problems for carnivorous plants.
Carnivorous plants can attract, catch and digest insects and other small animals with their transformed leaves. Depending on the species, the trapping methods range from sticky glandular hair to folding traps to trapdoor-like suction devices. They use the nutrients obtained in this way for their growth. In this way, the plants compensate for the lack of nutrients in their nutrient-poor locations.
All types of threat status recorded
For their survival, the special plants are dependent on such nutrient-poor and mostly moist locations. Typical habitats are moors, clean spring brooks, nutrient-poor waters, tropical rainforests or wet rocks. However, it is precisely these habitats that are becoming increasingly rare. In order to get an idea of the extent of the threat, an international research team led by Adam Cross from Curtin University in Western Australia has classified all carnivorous plant species according to the Red List categories of the International Commission on Species Conservation (IUCN) for threatened species.
As part of their work, they recorded the distribution areas and habitats of all 869 known carnivorous plant species and identified threats and risks of extinction. To do this, they examined factors such as changes in habitats, invasions of species, environmental pollution and climate change. “Through our work we were able to record 100 percent of all globally known carnivorous plants together with their red list nature conservation status,” says Cross’ colleague Andreas Fleischmann. “This quota is particularly gratifying, as we only know about ten percent of the approximately 300,000 flowering plants known around the world.”
Species are endangered in all plant genera
The result: “Our study has shown that around 25 percent of all known carnivorous plants today have an increased risk of extinction,” reports Cross. Examples of species threatened with extinction are in particular all species of the carnivorous plant genus Philcoxia, some of the pitcher plants (Nepenthes) and species of butterflies (Pinguicula). In addition, the scientists classified at least some species of all genera as endangered – they counted a total of 47 species. Another 104 are considered vulnerable.
A look at the distribution areas also revealed a clear pattern: “Organized by country, most of the carnivorous plants threatened with extinction can be found in Brazil, followed by Indonesia, the Philippines, Cuba, Thailand and Australia,” explains Cross. “These countries have a special responsibility for maintaining the global biodiversity of carnivorous plants. These are mainly species that usually only occur in a small area in these respective countries. “
Greatest threat from agriculture and urban development
But what are the causes of this threat? Based on their analysis, the researchers found that, globally, intensive agriculture is one of the greatest threats. As a result of the land use and the increased nutrient input, the habitats of around 170 of the plant species are currently disappearing. “Another problem is the area-wide over-fertilization of the landscape with nitrogen from the air, as it comes from dust from industry, traffic and agriculture. There are places in Germany where almost ten kilograms of nitrogen per hectare rain on the ground every year – even in remote bog locations, ”explains Fleischmann. “This becomes a problem especially for sensitive specialists.”
Construction projects and the expansion of cities – such as in Perth, Australia – pose a significant threat to carnivorous plants: in some regions, settlement development and the associated clearing led to the loss of more than 97 percent of natural vegetation. Green spaces along roads and railroad lines are usually the only remaining habitat for the carnivorous plants. In the long term, the research team expects that environmental changes due to climate change will also lead to the extinction of many carnivorous plant species. Pronounced periods of heat and drought are already causing problems for around 160 of the plants that depend on moist soil and regular water supplies. According to research, invasions of exotic grasses and pollution of the environment are already affecting 130 of the carnivore species.
Plant loss is irreversible
“Many of the threatening processes identified affect entire populations and cause rapid and often irreversible changes in ecosystems and biological processes,” the researchers summarize. “Our study forms an important basis for maintaining and protecting the diversity of this group of plants.” According to estimates by the researchers, some of the ecologically unique plant species will soon become extinct without the involvement of international organizations and nature conservation associations.
Source: Bavarian State Natural Science Collections, Article: Global Ecology and Conservation, doi: 10.1016 / j.gecco.2020.e01272