Habitat Changes at Lewa Wildlife Conservancy,Kenya. From cattle ranch to conservation area: effects of changing management on habitat from 1962-2006
Lewa Wildlife Conservancy
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Abstract: In 1979-80,Lex Linsen and the first author of this report (Wim Giesen),carried out the first comprehensive study of the vegetation of â??Lewa Downsâ?? (Linsen & Giesen,1983),a 180 km² farm in central Kenya run by the Craig family. The main economic activities at Lewa at the time included cattle and sheep herding,but also market gardening,wildlife conservation and game viewing â?? â??ecotourismâ?? before the word was invented. Since then there have been significant changes. Lewa has become a Wildlife Conservancy run by a board of trustees,and conservation of endangered species â?? especially black rhinos and Grevyâ??s zebra â?? are its main focus. In 1979-80,Lewa had few fences,as cattle were herded in a traditional way by local herders and were corralled in a boma (or thorn bush enclosure) at night for protection against predators. As a result of a lack of fencing and protection against poachers,wildlife sought refuge in the area and their numbers on the property significantly increased. When Lewa became a refuge for rhinos in the early 1980s,fencing was partly reintroduced to prevent rhinos from leaving Lewa and straying into areas where they could easily be poached. Gradually â?? especially after the Wildlife Conservancy was established in 1995 â?? more fencing was reintroduced,and currently the whole conservancy is fenced,with a few â??rhino-proofâ?? gates remaining to allow other wildlife to migrate in and out. Other changes since 1979-80 include an increase in the number of tourist camps in the area,and an increase in the road network. There has also been a very significant increase in the human population around Lewa. In the (now distant) past this was a major challenge,but now it has been turned into an opportunity thanks to various cooperative programmes with Lewa that include schooling,job opportunities,controlled dry season grazing by local community cattle and community-based ecotourism. Lastly,uncontrolled fires occurred regularly two decades ago,but nowadays controlled burning is part of Lewaâ??s management strategy,although irregular accidental fires still occur. The significant changes in management of Lewa have resulted in changes in various habitats. This was immediately apparent when the first author revisited Lewa in 1999,as certain well-known sites had altered â?? vegetation in some areas was more open,whereas at other locations it appeared denser. In discussions with Ian Craig,executive director,the idea was developed to carry out a comparative study of the vegetation to assess what had changed since 1979-80,with the aim of identifying trends and providing recommendations for management. LWC provided digital copies of aerial photographs of the area dating from 2000,which together with the earlier hard copy photographs of 1975 and the 1979-80 study,form the basis for the present proposed study. As described by Birkett (2003) savanna ecosystems in East Africa are rarely stable and can experience rapid local changes from dense woodlands to open plains. The Serengeti-Mara plains,for example,have fluctuated from open grassland to dense woodland and back to open grassland over the past century,with tree cover declining rapidly in the 1950s. While studies have focussed on elephant and fires,the precise cause of such dynamic changes has been the subject of considerable discussion and remains unclear. Similarly,loss of tree and shrub cover in the Amboseli basin since the 1960s has focussed on rising water tables and rising temperatures (Altmann et al.,2002). At the nearby Sweetwater Black Rhino Reserve in Laikipia,25% of Whistling Thorn Acacia drepanolobium died in just five years as a result of a combination of low rainfall and heavy browsing by elephants,black rhinos and giraffes (Birkett,2003). The present study aims to assess the magnitide of changes,and help clarify the cause of habitat changes at Lewa.