PATCH FOREST PROJECT
Forest fragmentation can have adverse effects on species richness and population size. The diversification of land use creates a mosaic landscape with increased isolation of wildlife and potentially hostile habitat in-between. Unlike natural landscapes, man-made patches are modified to form harsh edges unsuitable for wildlife. In addition, forest isolation can subdivide populations thereby reducing species interactions and creating a loss in genetic diversity.
In Sri Lanka, almost all primary rainforest has been destroyed, reduced from 80% to 20% in the past 80 years1 as a result of current and historic land use practices. The high rate of deforestation began in the Colonial Period when forest was named ‘Crown Land’ and timber was exported to make way for cash crops such as rubber, coconut and tea. More recently, increased agricultural production fuelling Sri Lanka’s plantation dominated economy has been a major contributing factor to the fragmentation of forest cover. The Mahaweli Project of 1969 involved large-scale irrigation of the dry zone for agricultural use, particularly for rice fields. In the 30 years of its implementation, 4% of the total land area of Sri Lanka was deforested2. Overall population increase has led to a demand for expanded slash and burn cultivation, large scale vegetable plantations and agricultural lands, further fragmenting the landscape and creating patched forests.
Research into patch forests is vital as it allows us to understand the importance of this remaining cover for wildlife diversity and movement. Using tracking methods we can investigate species presence as well as movement patterns. Extending our knowledge of local patch forests thereby helps us to understand the ways in which local wildlife are adapting to changing circumstances and also helps identify hostile areas that are limiting genetic diversity.
The WWCT has been conducting research on Central Highland patch forests such as the Dunumadallawa Forest, Kandy; Agra Arboretum, Agrapatana; Duckwari patch forest, Matale and Dunkeld Estate, Dick Oya. As well dry zone patch forests in the Gal Oya complex, Dehigaha Ela and Pidurangala, Sigiriya are also now being researched.
Results from previous research highlight the importance of small patch forest areas and corridors for all local species. Island residence means that local wildlife has little opportunity to move when faced with change and adversity. Instead, animals are forced to adapt and research is showing that patch forest cover is vital for this process to take place. Although overall biodiversity has not been overtly affected, individual species classes show low rates of diversity in some patch forest areas3. Leopards have been recorded residing and breeding within forest areas as small as 5km2 in addition to fishing cats, rusty spotted cats and various mammalian prey species.
With little contiguous cover remaining, it is proving essential that patches of forest be protected in order to increase patch connectivity and size and allow for dispersal and breeding and long-term persistence of wildlife species.
For example corridors, stretches of narrow habitat cover of varying types, (both forest and other plantation) that link forest areas, are being used by leopards to move between forested patches aiding in dispersal, reducing isolation and increasing genetic diversity.
The Patch Forest Project is an opportunity for WWCT researchers to further investigate the means by which local wildlife species are adapting to these human induced changes and the effects that they are having on population diversity. For land owners of small patch forests it is an opportunity to link with WWCT to better understand the role their land could be playing in the larger system and improve overall habitat for wildlife. With continued research, we can understand in more detail the importance of patch forests and corridors thereby highlighting their importance in our limited island ecosystem.