Is Climate Change the leading cause of species extinction in SL?

Rising temperatures caused by global warming have created a wide range of environmental problems, affecting not only humans but also the biodiversity spread across different ecosystems.  We are going through the sixth mass extinction, the only extinction in history caused by human activities.

The Climate Fact Checks team investigated how this has affected the biodiversity in Sri Lanka. After all, the country is a biodiversity hot spot, and we have a lot to lose.

Species that went extinct during the last decade in Sri Lanka

Numerous stressors, including climate change as the leading factor, are responsible for the vast extinction of species, and it has become a hot topic even in Sri Lanka. Some endemic species face extinction as a result, despite having thrived in similar climatic circumstances. Therefore, it is essential to maintain the ecosystem balance and understand the effects of global warming to develop adaptation measures required to predict the dynamics of ecosystem change and species extinction.

The diverse island of Sri Lanka is home to many flora and fauna, some endemic and having considerable richness of biodiversity compared to other regions of the globe. The many species of the animal range consist of 123 mammals, 526 birds, those who reside on the island and migrate, 9 turtles and tortoises, 104 types of lizards, 2 types of monitors, 104 snake species, 2 types of crocodiles, 336 Pteridophytes and 3,154 flowering plants. With 1,620 km of coastline, rich marine, and coastal biodiversity is also represented, notably including 208 species of hard coral and 756 species of marine molluscs. In addition, more than 1,300 marine fish species have been reported in Sri Lankan waters. It is astounding that such a small island is home to many species, according to the IUCN red data list of Sri Lanka.

With rapid development, urbanization, and global warming, there is a threat to all wildlife in Sri Lanka which is why the IUCN, the International Union for the Conservation of Nature, maintains a “red list” that notes down the animals that are at threat of extinction. The list of Extinct species in Sri Lanka – beyond reasonable doubt that the species is no longer extant according to the IUCN Red List was last updated on 2019-09-14. According to that, 20 amphibians and 01 plant species have become extinct. In addition, IUCN Red List shows the extinction of one frog species in 2020 listing. However, this list contains only species assessed for the IUCN Red List. Therefore, it is not representative of all the species in the country.

However, at least three of the five plant species thought to have gone extinct in Sri Lanka have been rediscovered. It was a Sri Lanka legume, Crudia zeylanica, and two flowering plants, Renaulia bengalensis, and Renoria decora,by field scientists in 2019 and 2020.

In addition, these plants were rediscovered outside protected areas which led botanists to believe that rare plants could still survive in small natural patches among urban settlements; despite this, the recently published national red list of the conservation status of the flora shows that threats to Sri Lanka’s plant life have gotten worse in the past eight years. According to the  National Institute of Fundamental Studies, at least 130 species of flora have not been observed in the last century and are therefore suspected of having gone extinct. The 2012 red list observed that roughly 44 percent of indigenous plants are threatened. Still, by 2020 that number has increased to 48 percent, a rate which has raised concern among environmentalists and botanists in the country.

However, many of them live on the borders of these parks and even, in some cases, in urban cities. To fall under the “Critically Endangered” column in the Red List of IUCN, the animal needs to meet two criteria: a reduction of less than 80% of the species in the last decade and a population of under 250 in an area. 

Species most threatened according to the IUCN Red Data book

However, Sri Lanka’s unique biological diversity is facing a general decline. Twenty-seven percent of 240 identified species of birds are threatened. In particular, one of Sri Lanka’s flagship species (elephant) has been affected by a population decline in dry and wet zones. It shows that a population of 10,000 at the turn of the century has dwindled to a mere 3,000 today. As for flowering plants, 1,385 species of the 3,154 identified species are classified as threatened, most of which (594) are endemic to Sri Lanka.

According to the IUCN Red Data book 2022, 7 animal species are Critically Endangered, 25 are Endangered, and 9 species have been identified as Vulnerable, including insects, mammals, amphibians, reptiles, and Aves. Some of them are Sri Lankan Clubtail, Sri Lanka warm snake, Sri Lankan Shrew, Red Slender Loris, Horned Lizard, Blue Magpie, etc.

Leading causes that threaten species in Sri Lanka

The main drivers that directly affect biodiversity include habitat loss, fragmentation, degradation, overexploitation of biological resources, loss of traditional crop and livestock varieties and breeds, pollution, human/wildlife conflicts, the spread of alien invasive species, and increasing human population density. Habitat loss and deforestation is the most severe threat to terrestrial biodiversity, with the island having lost approximately 50% of its forest cover within about 50 years. In marine and coastal ecosystems, coral mining for the lime industry has caused extensive damage to coral reefs, while other serious threats include the conversion of coastal habitats, destructive fishing practices, pollution from ships, and adverse impacts from land-based activities.

The area covered by closed canopy-dense natural forests declined markedly from 44% to 26.6% and 23.8% of the land area in 1983 and 1992, respectively, and 22.5% in 1999. However, as a result of various conservation measures, the rate of deforestation dropped to 20,000 ha per year between 1994 and 1999, revealing that the trend in forest loss had considerably slowed down, although it was continuing, nonetheless. Read more about the forest cover in Sri Lanka here.

According to the National Red List of Sri Lanka: Assessment of the Threat Status of the Freshwater Fishes of Sri Lanka 2020, Deforestation in catchment areas and removal of stream and riverbank vegetation are prime drivers of loss that affects freshwater fish in the wet zone. Such deforestation will result in significant changes in water flow regimens. In addition, removing streamside or riverine vegetation will enhance soil erosion, increase sediment flow into streams, change water quality, and alter stream beds; river diversion, over-exploitation, and exotic species can impact the breeding and foraging ecology of many freshwater fish species.

Meanwhile, scientists have observed that an increased habitat loss and clearance of forest threats to pollinators such as bees and the spread of invasive flora due to climate change are the fundamental causes of this biodiversity decline.

How Climate Change impacts Species Extinction.

UN Climate Change News, on 6 May 2019, reported, ‘Nature is declining globally at rates unprecedented in human history, and climate change is amongst the five direct drivers of change in nature with the most significant relative global impacts so far. This is one key finding of a landmark new report from the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES). The report finds that the distribution of 47% of the proportion of world terrestrial flightless mammals and 23% of threatened birds may have already been negatively impacted by climate change. Even for global warming of 1.5 to 2 degrees Celsius, most terrestrial species ranges are projected to shrink profoundly. 

In a study published Monday in the journal Nature Climate Change, researchers concluded that the Iberian lynx, an already critically endangered species that once flourished in parts of Spain, France, and Portugal, is likely to succumb permanently to decades of overhunting, habitat loss, disease and, in a final decisive blow, climate change. In addition, Earthyday organization shows 10 animals threatened by climate change, including bumblebees, whales, elephants, oceanic birds, apes, and any species declining due to climate change.

WWF scientists have estimated that most species on this planet (including plants) will have to “move” faster than 1,000 meters per year to keep within the climate zone they need for survival. Many species will need more time to redistribute themselves to keep up with the coming changes.

( With inputs from Nuwandhara Mudalige )