Graph of the Day: Mammal, Bird, and Amphibian Declines by Cause

Red List Index (RLI) for (a) birds, (b) mammals and (c) amphibians showing trends driven by the impacts of invasive alien species (IAS)  compared with trends driven by other factors, for the proportion of species expected to remain extant in the near future without additional conservation action; n = 9,785 nondata deficient extant bird, 4,555 mammal and 4,417 amphibian species at start of period. The differently shaded bands illustrate the contribution of different drivers to the overall decline in the RLI over the relevant period. Gland, Switzerland (IUCN) – Invasive Alien Species, ranging from disease and plants, to rats and goats, are one of the top three threats to life on this planet, according to a new publication coordinated by the Global Invasive Species Programme (GISP), of which IUCN is a partner. Most countries have made international commitments to tackle this threat, but only half have introduced relevant legislation and even fewer are taking adequate action on the ground. The publication, Global indicators of biological invasion: species numbers, biodiversity impact and policy responses [pdf], looked at 57 countries and found that, on average, there are 50 non-indigenous species per country which have a negative impact on biodiversity. The number of invasive alien species ranged from nine in Equatorial Guinea to 222 in New Zealand. A total of 542 species were documented as invasive aliens, including 316 plants, 101 marine organisms, 44 freshwater fish, 43 mammal, 23 bird and 15 amphibian species. According to Prof. Melodie McGeoch, lead author on the publication and member of the Centre for Invasion Biology, these numbers are a significant underestimate. “We showed that regions with low development status and little investment in research have lower than expected numbers of invasive aliens”. An increase in the number and spread of alien species, which adversely affect the habitats they invade, is nonetheless attributed to a substantial rise in international trade over the past 25 years. “While some threatened species on the IUCN Red List have improved in status as a result of successful control or eradication of invasive alien species, a growing number are more threatened owing to increasing spread and threats from non-indigenous species,” says Dr Stuart Butchart from BirdLife International. “This shows that although we are winning some battles in the fight against invasive species, current evidence suggests that we are losing the war.” “It’s likely to be more cost effective to prevent the spread of invasive species in the first place than to tackle the biodiversity crisis once they have become established,” says Dr Bill Jackson, IUCN’s Deputy Director General and Chairman of GISP. …

Impact of nature’s invading aliens measured for first time [pdf]