Sri Lanka is a small island with an unusually large share of Earth's biological variety. Together with the Western Ghats of India, it is recognized as one of the world's 36 biodiversity hotspots because it has many endemic species and serious habitat threats. Its rainforests, mountains, rivers, dry forests, wetlands, and coasts create many different niches in a compact area.
This makes Sri Lanka an important natural laboratory for studying evolution, ecology, and conservation.
Island isolation helps explain why so many Sri Lankan species are found nowhere else. When populations are separated from mainland relatives, mutation, natural selection, genetic drift, and local adaptation can produce new species over long periods of time. Wet-zone forests such as Sinharaja protect many endemic birds, amphibians, reptiles, plants, and mammals, including the purple-faced langur.
Conservation is urgent because habitat loss, fragmentation, invasive species, pollution, and climate change can eliminate small-range species quickly.
Key Facts
- A biodiversity hotspot must have at least 1,500 endemic vascular plant species and have lost at least 70% of its original natural vegetation.
- Endemism means a species is native to and restricted to a specific geographic area.
- Sri Lanka and the Western Ghats of India form one global biodiversity hotspot.
- Species richness = the number of different species in a given area.
- Endemism rate = endemic species / total native species x 100%.
- Habitat fragmentation reduces gene flow, and lower gene flow can increase extinction risk in small populations.
Vocabulary
- Biodiversity hotspot
- A region with very high numbers of endemic species that is also under severe threat from habitat loss.
- Endemic species
- A species that naturally occurs in only one particular place and nowhere else in the wild.
- Wet-zone rainforest
- A warm, high-rainfall forest ecosystem in southwestern Sri Lanka that supports many specialized and endemic species.
- Habitat fragmentation
- The breaking of a large continuous habitat into smaller isolated patches, often by roads, farms, towns, or plantations.
- Speciation
- The evolutionary process by which populations become genetically different enough to form new species.
Common Mistakes to Avoid
- Thinking a hotspot means a place with warm climate, which is wrong because the term refers to high endemism plus severe habitat loss.
- Confusing native and endemic species, which is wrong because a native species can occur in several regions while an endemic species is restricted to one region.
- Assuming small islands have low biodiversity, which is wrong because varied habitats and long isolation can create many niches and high endemism.
- Counting only large mammals when judging biodiversity, which is wrong because plants, insects, amphibians, reptiles, birds, fungi, and microorganisms are major parts of an ecosystem.
Practice Questions
- 1 A forest survey records 240 native plant species, and 96 of them are endemic to Sri Lanka. Calculate the endemism rate as a percentage.
- 2 A rainforest patch originally covered 1,200 square kilometers, but only 300 square kilometers remain. What percentage of the original habitat has been lost?
- 3 Explain why an isolated island with mountains, rainforests, rivers, and coastal habitats can develop many endemic species over evolutionary time.