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.
Understanding Sri Lanka, a Biodiversity Hotspot
Sri Lanka’s living diversity is shaped by steep environmental changes across short distances. The central highlands are cooler and wetter than much of the lowlands. Monsoon winds bring rain at different times to different sides of the island.
Rock type, soil depth, sunlight, and stream flow vary from place to place. A forested ridge can hold conditions very different from a nearby valley. Plants respond to these local conditions first.
Insects, frogs, birds, and mammals then depend on the plants, shelter, and food available there. This is why protecting one type of forest cannot replace protecting every habitat type.
Many endemic organisms have very small distributions. Some may live only in a few forest patches, one mountain range, or a particular stream catchment. Amphibians are especially sensitive because their skin loses water easily and many lay eggs in clean, moist places.
If a cloud forest becomes warmer or drier, a frog adapted to that cool habitat may have nowhere nearby to move. Small populations face further problems.
A disease outbreak, severe drought, landslide, or fire can affect most individuals at once. Genetic diversity is important here because it gives a population more variation that may help some members survive new conditions.
Biodiversity is not only a list of rare species. It is a network of relationships. Flowering plants need pollinators such as insects, birds, or bats.
Fruit-eating animals move seeds into gaps where new plants can grow. Predators limit the numbers of some prey species. Fungi and bacteria return nutrients from dead material to the soil.
When one part of this network declines, effects can spread through the ecosystem. Healthy forests in Sri Lanka also help slow water runoff, reduce soil erosion, and protect streams used by nearby communities. Forest loss on slopes can increase muddy water, flood risk, and pressure on farms downstream.
Conservation works best when it considers whole landscapes rather than isolated protected areas. Forest corridors can allow animals and plant seeds to move between patches. Riverbank vegetation can protect water quality while giving wildlife a route through developed land.
Scientists use field surveys, camera traps, sound recordings, and DNA studies to find species and estimate population changes. Students should pay attention to the difference between a species being present and a species having a stable population. A few sightings do not prove that a population is safe.
It is useful to notice local actions too. Reducing plastic waste, avoiding the release of unwanted pets, protecting native trees, and reporting wildlife observations can support conservation knowledge and reduce harm.
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.