Secretary bird (Sagittarius serpentarius) in Ngorongoro Crater, Tanzania (East Africa). Photo by: Rhett Butler.
What started as a program aimed at land redistribution to empower vulnerable, landless people has turned into an ecological quandary. In many parts of Zimbabwe, commercial agriculture has given way to small-scale farming. A new study published in Mongabay’s open-access journal Tropical Conservation Science shows that the change has profoundly disrupted the ecosystem in at least one critical wildlife habitat, the Driefontein grasslands Important Bird and Biodiversity Area (IBA).
In 2000, President Robert Mugabe implemented a controversial "fast track" land redistribution program that took land from white farmers and handed it over to black farmers, with the aim of rectifying the expropriation of land from black Zimbabweans during the pre-1980 colonial era. In many cases, local people occupied farms regardless of whether or not they had been officially designated for resettlement, and vast tracts of land outside farms were cleared for agriculture. The program was characterized by violence and chaos, and has been widely criticized as having undermined the nation’s food security and economy.
To see whether these changes also posed a threat to ecosystems, as biologists suspected, a team led by researchers at the University of Zimbabwe analyzed satellite images taken of the Dreifontein IBA in 1995, 2000, 2005, and 2010.
More than 12,000 IBAs have been designated as such by the U.K.-based NGO BirdLife International because they are internationally significant for the conservation of birds and other biodiversity. But despite their biodiversity value, many IBAs lack legal protection and are threatened by human activities, such as agriculture, forestry, and settlement.
That’s the case at the Driefontein IBA, a 20,000-hectare region of open, wet grassland located on Zimbabwe’s central plateau that BirdLife International has designated as "In Danger." The soils are sandy and fast draining, making the area unsuitable for farming. Until the onset of the land redistribution program, the IBA was divided into large commercial cattle ranches. Currently about 17,000 people live there.
The satellite images revealed that between 1995 and 2010, nearly 5,300 hectares of grassland and wetland were lost— more than one-quarter of the total IBA. At the same time, cultivated land expanded by almost 4,200 hectares. The study concludes that the loss of natural habitat was largely driven by the increase in farming, following the resettlement of people within Driefontein.
The Driefontein IBA supports three globally threatened bird species that use wet grasslands as habitat: the wattled crane (Bugeranus carunculatus), the grey crowned crane (Balearica regulorum) and the secretary bird (Sagittarius serpentarius). The authors express concern that the damage to the area’s habitat could negatively impact these species, particularly the two cranes, which in Zimbabwe are designated "Specially Protected" species and are largely restricted to Dreifontein.
The area of Dreifontein habitat converted to agriculture translates to a loss of about three home ranges and 212 breeding sites for wattled cranes. Such losses increase the risk of local extinction of bird populations.
The authors state that the habitat degradation they document threatens humans as well as birdlife. Dreifontein wetlands are the main water supply for rivers that support a significant number of people living downstream, as well as biodiversity. “Threats to birds and wetlands habitats are also threats to human livelihoods because people in this semi-arid area depend on wetland ecosystem services for their survival,” the authors write.
Further adding to the conundrum is a growing human population. “It is likely that with increasing human population the natural habitat of the study area will be degraded further,” the authors write.
However the authors do believe that if well managed, Dreifontain IBA’s mosaics of agricultural land can support a range of bird species. Although the authors write that further study is needed to document the effect of changing land use on the area’s birdlife, they propose the development of a strategic land use plan in order to reduce the loss of sensitive wetland habitats and biodiversity in Driefontein IBA.
- Fakarayi, T., Mashapa, C., Gandiwa, E. and Kativu, S. 2015. Pattern of land-use and land cover changes in Driefontein Grassland Important Bird Area, Zimbabwe. Tropical Conservation Science Vol.8 (1): 274-283.