Conservation of carnivorous plants in the age of extinction

Abstract

Carnivorous plants (CPs)—those possessing specific strategies to attract, capture and kill animal prey and obtain nutrition through the absorption of their biomass—are harbingers of anthropogenic degradation and destruction of ecosystems. CPs exhibit highly specialised and often very sensitive ecologies, being generally restricted to nutrient-impoverished habitats where carnivory offers a competitive advantage. As such, they are often the first species to disappear following habitat degradation, land use change, and alteration to natural ecological processes, and are at significant risk from processes such as eutrophication and weed invasion, and even poorly-understood impacts such as airborne nitrogen inputs. Many of the world's 860 species of CPs are found in wetland habitats, which represent some of the most cleared and heavily degraded ecosystems on Earth. Global diversity hotspots for CPs are likewise located in some of the most heavily cleared and disturbed areas of the planet—southwestern Western Australia, Southeast Asia, Mediterranean Europe, central eastern Brazil, and the southeastern United States—placing their conservation at odds with human developmental interests. Many carnivorous plant species exhibit extreme range-restriction and are wholly localised to specific geological formations, microhabitats or elevations, with nowhere to move to in the face of environmental change, such as a warming, drying climate. We provide the first systematic examination of the conservation status and threats to all CPs globally, compiling full or partial assessments of conservation status category for 860 species from 18 genera, and provide ten recommendations towards better conservation and management of this iconic group. A total of 69 species were assessed as Critically Endangered (8% of all species), 47 as Endangered (6%), 104 as Vulnerable (12%), and 23 as Near Threatened (3%). Slightly over 60% of CPs (521 species) were assessed as Least Concern. At least 89 species are known from only a single location based on current knowledge. Data on threatening processes were available for 790 species, with the most common threatening processes including Agriculture and Aquaculture (impacting 170 species), Natural Systems Modifications (168 species), Climate Change and Severe Weather (158 species), Energy Production and Mining (127 species), Human Intrusions and Disturbance (126 species), and Biological Resource Use (98 species). Almost a quarter of all species were impacted upon by three or more threatening processes. The most significant threats placing species at imminent risk of extinction include the continuing clearing of natural habitat for urban and agricultural development and the illegal collection of individuals from the wild for horticultural trade. The complex and specialised ecological requirements of CPs, together with the multifaceted threats they face, make conservation difficult and repatriation even to restored areas challenging. As the number of vulnerable, endangered and extinct carnivorous plant species continues to grow, despite significant conservation efforts in many regions and greater awareness of their ecological requirements, it is clear that a paradigm shift is required in our approach to the preservation of this unique group of plants in order to achieve long-term conservation successes.