Posts Tagged ‘Boiga ceylonensis’
Dry Zone in a Biodiversity Hotspot
A collage of Sri Lanka’s dry zone species and habitats (SE coast near Kumana).
Sri Lanka’s climate zones, split between the wet, intermediate and dry zones each have distinctive qualities and biodiversity. While the wet zone has the highest levels of endemism the dry zone shows close affinity to southern India’s flora and fauna. There are even several slivers of the island with arid climates that are sometimes separated from the dry zone (the Jaffna peninsula, Mannar, Yala etc.). On several trips in the last year, and most importantly the summer during the pandemic, I continued to explore, document and better understand the biodiversity and landscapes of the dry zone.
Although the extent of the dry zone covers nearly two thirds of the island it is not a homogenous landscape and there are significant variations in terrain, forest cover, hydrology and land use in its different parts. The area is characterized by seasonal spells of intense rain (the monsoon) and longer periods with relatively little rain. The North-East (winter) Monsoon, active from October to January, provides most of the seasonal moisture. This June we traversed the three climate zones: we left Colombo in the midst of showers from the South West Monsoon, experienced rain in the intermediate zone near Sigiriya and then had almost all rain-free dry days in Trincomalee, Batticaloa and Arugam Bay.
Panthera pardus kotiya at Wilpattu National park. Leopards are not exclusive to the dry but the large protected areas of Yala, Kumana and Wilpattu offer the best places to encounter them. This juvenile male thrilled our small group with a lengthy encounter in the early morning of a visit in July. Special thanks to Achintha Piumal who alerted us to its presence and got us to the location without disturbing his morning rituals.
Conservation Value of the Dry Zone
The lengthy Western Ghats/Sri Lanka biodiversity hotspot, as demarcated by CEPF, is characterized by India’s west-coast mountainous spine as well as (almost) the entire island of Sri Lanka. It always intrigued me that the Western Ghats portion is made up of mountainous habitats while Sri Lanka’s portion includes significant lowland, plains areas in its dry zone along with its Central Highlands and coastlines. In fact, all of Sri Lanka, with the exception of the Jaffna peninsula, falls under the hotspot boundary. It’s a somewhat arbitrary boundary distinction and meant to give a target area for the governments of India and Sri Lanka to value and protect. The Western Ghats plains areas in the shadow of the ghats have been largely converted to agricultural and other human-dominated landscapes. In contrast Sri Lanka’s lowlands, especially in the dry zone, still have large areas of natural forest cover and this most likely explains the boundary choices.
The largest protected areas in Sir Lanka, the ones that draw visitors wanting a “safari” experience, are all found in the dry zone. Yala National Park in the south-east draws the largest numbers of visitors. Its north-eastern parts, bisected by the Kumbuk Oya, are protected as Kumana National Park. In the central plains around Dambulla/Sigiriya parks protected as part of irrigation reservoirs such as Minneriya, Kaudulla and Kala Wewa host some of the biggest congregations of Asian elephants in the world. Sri Lanka’s largest national park is Wilpattu located on the Gulf of Mannar and stretching nearly to the center of the island at Anuradhapura. After being contested during the years of fighting, Wilpattu has made a comeback. Classic dry zone mammal species like sloth bears, elephants, grey langur, spotted deer are all found at Wilpattu. I appreciate Wilpattu for its forests. Visitors spend hours traversing mature strands of tropical evergreen forest to get to the open areas and wilus (shallow natural lakes that can either have saline or fresh water) areas with bird and mammal densities. There are many significant species of trees on the drive in. I appreciate the Manilkara hexandra (or palu/palai) that are a favorites species for birds of prey, Malabar Pied Hornbills and occasionally, leopards.
Many of the other large protected areas of Sri Lanka including Wasgamuwa, Gal Oya and Madhura Oya and Somawathiya are all in the dry zone. Satellite imagery shows large tracts of dry zone forest north of Vavuniya in the Vanni. These were areas that were controlled by the LTTE for many years and survived the ravages of war. At this stage few of these are being explored by wildlife enthusiast and birders, as far as I know.
Granite rocky outcrops are a feature of many parts of Sri Lanka’s dry zone. The Kudumbigala hermitage on the edge of Kumana National Park has some exquisite rocks that are safe from those blasting and quarrying.
Connections Across the Straits
Ecologists and others familiar with the plains of Tamil Nadu and Sri Lanka’s dry zone have observed the remarkable similarities in climate, soil and geology. It is certainly something I think about every time I fly into Madurai and drive away from this ancient urban settlement. The red soil and occasional patches of thorn forest and sacred Ficus trees, scattered amongst drought-prone fields and granite outcrops, hint at a past that would have looked quite different.
Rom Whitaker, India’s snake man who is based in Tamil Nadu, visited Colombo in 2010 and gave a public talk sponsored by Dilmah Conservation that reminded me of the connection between Sri Lanka and Tamil Nadu. He drew our attention to the fact that Sri Lanka’s dry zone coastal areas were likely representative of what Tamil Nadu’s plains once looked like. Land cover change on the plains of Tamil Nadu, of course, has been happening at an astounding pace in recent decades. However, Rom was hinting at patterns that happened in India much earlier-as in hundreds if not thousands of years ago. Those changes led to a different landscape and perhaps a less-humid climate in plains Tamil Nadu. This topic deserves thorough academic investigation but Rom’s message was conservation- oriented. He was discretely pleading with the Sri Lankan audience to act to protect areas before sand mining, granite blasting, deforestation and other threats destroyed the remarkable magic of the dry zone.
The situation with Sri Lanka’s dry zone is especially remarkable because it historically experienced dramatic land cover change and then recovered. The ancient Sri Lankan hydraulic civilizations that created systems of sophisticated water management and irrigation more than 2300 years ago were all based in the dry zone. The remains of these civilizations and especially their Buddhist sites in places like Ruhunu, Anuradhapura and Polonnaruwa illustrate of the importance of the dry zone in Sri Lanka’s rich cultural history. It was only later, after repeated attacks and the outbreak of malaria, that the Sinhalese kings moved south-west into the wet zone. That migration left much of the dry zone alone and gave the forested areas a chance to recover. Mark Ashton, Nimal & Savitri Gunatilleke and others in fact state that “the early phases of Sri Lanka’s history therefore suggests that nearly all of the forests now in the dry zone are of secondary origin, having re-established over the last 7-8 centuries.” (Ashton et al. p.12)
The idea that the plains of Tamil Nadu might once have been thickly forested in a way similar to Wilpattu is intriguing. The land cover change and the clearing of these Indian forested areas would have happened so long ago that there are few records of the change. Great kingdoms and empires-the Pallavas, Pandians, Cholas and others-rose and fell over several millennia. Presumably the dry evergreen plains forest was cut back to make room for agriculture during these times. The relatively recent (and well documented) British colonial forestry efforts were focused on wooded, hilly areas like the Anamalais, Nilgiri and Palani Hills. A modern forest map of Tamil Nadu (see TN Forest Department) suggests that almost all forest cover is in the Western and Eastern Ghats rather than the plains and a few mangrove patches. There are relatively small examples of the dry evergreen forest in Tamil Nadu and there are efforts in Auroville (see link) to protect and propagate this forest type, but nothing on the scale of what is found across the straits in Sri Lanka.
Panthera pardus stretching at Wilpattu National park. Special thanks to Achintha Piumal who alerted us to its presence and got us to the location without disturbing his morning rituals.
SELECTED REFERENCES
Ashton, Mark et. al. A Field Guide to the Common Trees and Shrubs of Sri Lanka. Colombo: WHT Publications, 1997. Print.
Conservation International. Biodiversity Hotspots. Web.
Critical Ecosystem Partnership Fund. Biodiversity Hotspots. Web. (see link for Western Ghats projects)
Critical Ecosystem Partnership Fund.. Ecosystem Profile: Western Ghats & Sri Lanka Biodiversity Hotspot (Western Ghats Region). May 2007. Web.
De Silva, Asoka T., Ed. Sri Lanka’s Forests-Nature at Your Service. Colombo: Sri Lanka Association for the Advancement of Science, 2014.
Ministry of Mahaweli Development & Environment. Biodiversity Profile- Sri Lanka Sixth National Report to the Convention on Biological Diversity. May 2019. Web.
Ministry of Mahaweli Development & Environment. National Biodiversity Strategic Action Plan 2016-2022. May 2016. Web.
