Part two of Gehan de Silva Wijeyeratne’s look at the physical, evolutionary and human-induced forces that have contributed to this island’s biodiversity
Imagine your goal was to create the perfect location for wildlife tourism. Sri Lanka would be a good example how to go about it. You want to keep it small so that tourists don’t have to travel too far from one location to another. But not too small as small areas don’t have many animals and also cannot hold on to their animals. An island would be good as isolation allows species to evolve into new species. An ancient start would help.
So let’s begin with Sri Lanka being split off from ancient Southern Gondwana, tethered to India and drifting north on the Indian tectonic plate, carrying an ancient cargo of species which results in affinities between species in Madagascar and Sri Lanka. Next, crash the Indian plate into the Asian land mass (creating the Himalayas) and allowing Palaearctic mammals such as the tiger to drift south into India. Anchor Sri Lanka nearby as a continental island to enable immigration of species from the Asian mainland. But leave the island isolated for sufficiently long interglacial periods (where sea levels rise cutting off the island) for the process of speciation to allow endemics to evolve.
Isolation and physical stresses have resulted in high levels of endemism (e.g. 100% freshwater crabs, 95% amphibians, 80% land molluscs, 53% freshwater-obligate fish, 52% of dragonflies, 25% flowering plants, etc.). These have been supplemented by the ‘immigrants’ from later land bridge connections. The down-side of repeat connections is that Sri Lanka does not have as high a proportion of endemic species as found on an island such as Madagascar.
An Elephant herd in Minneriya. Pic by Gehan de Silva Wijeyeratne
Physical isolation is not enough and ecological isolation is also desirable, both from Asia and within the island. A good trick here is to create a central mountainous core, with two alternating and diagonally blowing monsoons (the South-west and North-east) creating a very moist ‘wet zone’, distinct from a ‘dry zone’. The mountains also allow for a further vertical zonation, allowing more speciation to take place as some species diverge into sister species at different altitudes. Horton Plains National Park, the roof of Sri Lanka has many species confined to the highlands. Build on this theme by up-thrusting a few more rugged, spectacular mountain ranges such as the Knuckles Wilderness creating elevated wet zone ‘islands’ within the wet zone. This creates point endemics such as the Tennent’s Leaf-nosed Lizard in the Knuckles.
For extra measure add a few mountainous edges to lowland rainforests like Sinharaja to create more point endemics like Karu’s and Erdelen’s Dragon-lizard in Eastern Sinharaja (15 of the 18 agamid or dragon-lizards are endemic). Indulge in more innovation by throwing up a mountain with a wet zone character, Ritigala, surrounded by a sea of dry zone with more point endemics and build a legend around it that it was a piece of medicinal herb rich mountain from the Himalayas dropped by the Monkey God Hanuman as told in the Indian epic of Ramayana. Culture and wildlife go hand in hand in this area of ancient kingdoms of Anuradhapura and Polonnaruwa, where the tallest archaeological brick buildings in the whole world, giant stupas, stand. Endemic Toque Monkeys wage ferocious tribal wars watched over by meditating saffron robed monks and are studied in one of the longest running zoological field studies in the world; the Smithsonian Primate Research project.
The process of speciation can be accelerated further by throwing in a few evolutionary tricks like direct development in the Rhacophorid Tree Frogs. This allows them to skip the stage of laying eggs in water and having tadpoles developing in water which leaves them vulnerable to periods when ephemeral bodies of water dry out. Instead, allow them to use foam nests in which the eggs develop into little frogs which plop out fully formed allowing one of the significant species radiations discovered in the 20th century to take place.
There are many other examples of species radiations; for example all 20 of the Forest damsels described so far from the island are endemic. In fact Sri Lanka has four, five, and six times as many species of dragonflies per unit area than New Guinea, Borneo and Madagascar respectively. Geological turmoil and variations in the climate creating ‘ecological niches’ could also have created physical stresses that favoured evolutionary variation. In fact, although I have referred to Sri Lanka’s land area as 66,000 km2 , most of the endemism is packed into an area of around 15,000 km2; less than a quarter of the total in what comprises the wet zone. This ‘localisation’ of small-range endemic species makes the endemicity (e.g. 740 endemic flowering plants in the wet zone) and the species richness in the wet zone even more remarkable.
Whilst all this is happening, keep stirring the evolutionary brew with fresh material. A few judiciously spaced out glaciations will lower sea levels forming a land bridge (Adam’s Bridge linking India to Mannar across the Palk Strait) allowing mainland species to immigrate and start anew to evolve into new species. Wildlife tourists like big stuff, so keep the land bridge open to get a good population in of the elephants, Leopards and Sloth Bears. Ooops! Closed it too soon as enough tigers did not make it across to establish a viable population.
Having got the big stuff in, one may as well make an eco-tourism spectacle out of it. This requires some human intervention or anthropogenic factors for the technically minded. Throw in a liberal sprinkling of ancient kings who will usher a golden age of hydraulic civilisation. They will dot the island’s dry zone with grand civil engineering works, with vast lakes (e.g. the Sea of Parakrama) irrigating agriculture. Allow this to go to ruin and perfect conditions are made for the Elephant Gathering at Kaudulla and Minneriya in the North-central Province where over 300 elephants may gather on the receding lakes in search of grazing, water, mates and social networking (elephants don’t use Facebook)! Allow the farmland in the South-east in Yala to turn to grassland where together with the man-made waterholes, conditions are perfect for high densities of Spotted Deer, in turn creating one of the highest densities of Leopards.
The over 2,000 man-made lakes or wewas create wildlife rich wetlands which pre-date the interventionist conservation efforts of the London Wetland Centre. In Yala at Buttuwa Wewa, this results in the largest seasonal concentration in the world of the Mugger or Freshwater Crocodile, the second largest land reptile in the world. Not far away, the soft sandy beaches are visited by five of the seven species of marine turtle including the Leatherback; a giant.
Introduce Buddhism and Hinduism, two great world religions with a respect for animal life. Most animals lose their fear of people and everything from Leopards in Yala, Blue and Sperm Whales to fighting Purple Swamphens in Talangama Wetland (close to the commercial capital Colombo) are embarrassingly curious and camera friendly for tourists.
With the top side sorted out, the marine side needs some attention as well. The trick here is to have deep water close to shore which suits the large whales (unlike an island like Britain which is covered with shallow seas or the islands of the Indonesian archipelago). Improve on this by having the continental shelf pinching in at the South at Dondra Head near the fishery harbour of Mirissa so that Blue Whales can be seen easily close to shore on a morning whale watch from a coastline studded with luxury villas, boutique hotels and backpacker crash pads. Create a deep 400m depth isobath running north- south for Sperm Whales in Kalpitiya (the Sperm Whale Strip of E 79 35 to E 79 40). Slide a peninsula of golden sandy beaches out onto it so that the Sperm Whales are a mere fifteen minutes by boat. For those for whom boats are not their thing thrust a deep submarine canyon into Trincomalee in the North-east so that Blue and Sperm Whales can be seen from ashore on some days from the temple atop Swami rock or very rarely from the pool side of beach hotels. For extra good measure throw in a few more canyons on the East coast which are good for enigmatic and elusive beaked whales. All of this is being a bit greedy as the island also has shallow seas where it needs it most; close to the mainland, to allow intermittent land connections for the immigrant waves to supplement the speciation factory. The island has the best of everything, in terms of underwater topography; now add to this a generous mix of nutrients.
Whales need food; lots of it. The two monsoons are in charge of the kitchen, driving a hundred and three river systems (yes, that’s right, 103) bringing down rich organic nutrients from the mountains, slow released from the lichen cloaked cloud forests to the lowlands creating nutrient rich soup around the island. The Blue Whales and the Cloud Forests are inter-connected. Not content with that, whip up some speed with the monsoons and create upwellings, which generate phytoplankton blooms which show up on Indian remote sensing satellites suspended in space in geo-synchronous orbits. All of this food creates fringing coral reefs which are rich in marine species. Sri Lanka which is 432km long has approximately 800 species of marine fish recorded. Sites better publicised for their marine wildlife such as the 1,126km long Gulf of California (Sea of Cortez) has 700 species of fish. The Maldivian islands which stretch across 1,500km have around 1,200 species recorded and the Great Barrier Reef stretching over 2,600km has 1,500 species. If we consider the number of marine fish species per unit length, we can see that Sri Lanka has roughly treble the statistic for the Gulf of California and double that for Maldives. This is a very crude measure but it helps to give a flavour to the layperson of the relative species richness.
The nutrient rich water in Sri Lanka and the monsoons which lash the shores reduce visibility in the water. The lack of good viewing has resulted in its species richness not being understood as almost everyone including dive operators in Sri Lanka think the waters are ‘poor’ for fish compared to other tropical destinations. I have come to realise that ‘poor viewing’ has been confused with ‘poor species richness’, which it is not.
To be clear about context, for big game safaris many countries in Africa are unmatched. Large tropical islands such as Madagascar and New Guinea, lack large land mammal herbivores such as elephants or large carnivores such as Leopards (Borneo does not have Leopards and the origin of its elephants is disputed) but in absolute terms of species have huge biodiversity. However, from the viewpoint of commercial wildlife tourism, in terms of ease of access, tourism infrastructure, affordability and with a short time frame of say two weeks, there is no country which has the array of terrestrial big game, endemism-rich species density, spectacular marine wildlife, diverse landscapes and close knit cultural bonds (love-hate with elephants) with wildlife that is found in Sri Lanka.
The proof of the pudding of the physical, evolutionary and human factors is in the viewing. A visit of mine in April 2012 is an example of good evidence. I had an amazing trip where in the space of two weeks I watched courting Blue Whales, scrumming Sperm Whales, had a mother and baby elephant pad silently past my vehicle and drove back to camp in the gathering dusk, passing Leopards out on the hunt.
In this article, I have with some speculation on my part drawn together material that is known from Sri Lanka and the mechanics of large scale processes studied elsewhere. Science is dynamic and what is known and conjectured today can change. But the broad principles should hold true and I hope I have explained why Sri Lanka deserves more attention from both those viewing wildlife for pleasure as well as those studying how planetary forces and time, drive the great engine of evolution and biogeographical distributions. At this point I should add a gentle reminder that in reality evolution is a ‘blind process’ although I have for the purpose of telling a story, written it as if evolution had set out to make a super-rich wildlife destination.
I have to add that although it is arguably the best all-round country for multi-faceted wildlife viewing with ease, it comes with a caveat. Sri Lanka does need improvement in terms of better interpretation and better facilities for visitors at parks and reserves and more responsible guiding. Finally and alarmingly, less than 8% of its biodiversity rich wet zone remains forested and more attention is needed both locally and internationally to lay emphasis on how special this island is for its wildlife.
Article by Gehan de Silva Wijeyerathne Via The Sunday Times