Report: Human activities have introduced 37,000 'alien species,' leading to biodiversity decline
In the most extensive study on invasive species carried out till date, the Intergovernmental Platform on Biodiversity and Ecosystem Services (IPBES) in its new publication – the “Assessment Report on Invasive Alien Species and their Control’’ – has found that there are 37,000 alien species, including plants and animals, that have been introduced by many human activities to regions and biomes around the world, including more than 3,500 invasive alien species and that invasive alien species have played a key role in 60% of global plant and animal extinctions recorded.
The report, which was released on Monday, said that invasive alien species are one of the five major direct drivers of biodiversity loss globally, alongside land and sea use change, direct exploitation of organisms, climate change, and pollution.
The IPBES released its report following a week- long plenary from August 28th, with representatives of the 143 member States which have approved the report. IPBES is an independent intergovernmental body established to strengthen the science-policy interface for biodiversity and ecosystem services, working in a similar way to the IPCC, which is the UN’s climate science body. The study, which has taken place over a period of four years, has been by 86 leading experts from 49 countries, drawing on more than 13,000 references.
The report has noted that the number of alien species (species introduced to new regions through human activities) has been rising continuously for centuries in all regions, but are now increasing at unprecedented rates, with increased human travel, trade and the expansion of the global economy.
“Not all alien species establish and spread with negative impacts on biodiversity, local ecosystems and species, but a significant proportion do – then becoming known as invasive alien species. About 6% of alien plants; 22% of alien invertebrates; 14% of alien vertebrates; and 11% of alien microbes are known to be invasive, posing major risks to nature and to people,’’the IPBES has said.
The report further noted that many invasive alien species have been intentionally introduced for their perceived benefits, “without consideration or knowledge of their negative impacts’’ – in forestry, agriculture, horticulture, aquaculture, or as pets.
Nearly 80% of the documented impacts of invasive species on nature’s contribution to people are negative.
“Invasive alien species have been a major factor in 60% and the only driver in 16% of global animal and plant extinctions that we have recorded, and at least 218 invasive alien species have been responsible for more than 1,200 local extinctions . In fact, 85% of the impacts of biological invasions on native species are negative,” said Prof. Anibal Pauchard, co-chair of the Assessment.
The water hyacinth is the world’s most widespread invasive alien species on land. Lantana, a flowering shrub, and the black rat are the second and third most widespread globally. The brown rat and the house mouse are also widespread invasive alien species.
The report said that the annual costs of invasive alien species have at least quadrupled every decade since 1970, as global trade and human travel increased. In 2019, the global economic cost of invasive alien species exceeded $423 billion annually.
“These trends are projected to accelerate as the global economy expands, land and seas are used more intensively, and demographic change takes place,’’the report said.
The reduction of food supply, has been cited by the report as the most common impact of alien invasive species. For example the European shore crab impacting commercial shellfish beds in New England or the Caribbean false mussel damaging locally important fishery resources in Kerala, by wiping out native clams and oysters. The Caribbean false mussel was originally from the Atlantic and Pacific coast of South and Central America, but are believed to have travelled to India via ships, later spreading to estuaries through smaller fishing vessels.
Invasive alien species like Aedes albopictus and Aedes aegyptii spread diseases such as malaria, Zika and West Nile Fever, while others also have an impact on livelihood such as the water hyacinth in Lake Victoria in East Africa led to the depletion of tilapia, impacting local fisheries.
The IPBES report has further warned that warming temperatures and climate change could favour the “expansion of invasive species’’.
“Climate change is also predicted to increase the competitive ability of some invasive alien species, extending the area suitable for them and offering new opportunities for introductions and establishment. Invasive alien species can also amplify the impacts of climate change.
For example, invasive alien plants, especially trees and grasses, can sometimes be highly flammable and promote more intense fires,’’it said.
The report found that 34% of the impacts of biological invasions were reported from the Americas, 31% from Europe and Central Asia, 25% from Asia and the Pacific and about 7% from Africa. Most negative impacts are reported on land (about 75%) – especially in forests, woodlands and cultivated areas – with considerably fewer reported in freshwater (14%) and marine (10%) habitats . Invasive alien species are most damaging on islands, with numbers of alien plants now exceeding the number of native plants on more than 25% of all islands.
Most countries (80%) have included targets related to managing invasive alien species in their national biodiversity plans. Only 17% specifically address the issue in national legislation, although more (69%) include it as a part of legislation in other areas. Nearly half of all countries (45%) do not invest in management of biological invasions.
In December last year, governments agreed to reduce the rate of introduction and establishment of invasive alien species by at least 50% by 2030 under target 6 of the Kunming-Montreal Global Biodiversity Framework.
