The decline of water hyacinth on Lake Victoria was due to biological control by Neochetina spp

There has been some debate recently about the cause of the decline of water hyacinth on Lake Victoria. While much of this evidence points to classical biological control as the major factor, the El Niño associated weather pattern of the last quarter of 1997 and the first half of 1998 has confused the issue. We argue first that the reductions in water hyacinth on Lake Victoria were ultimately caused by the widespread and significant damage to plants by Neochetina spp., although this process was increased by the stormy weather associated with the El Niño event; second that increased waves and current on Lake Victoria caused by El Niño redistributed water hyacinth plants around the lake; and third that a major lake-wide resurgence of water hyacinth plants on Lake Victoria has not occurred and will not occur unless the weevil populations are disrupted. We conclude that the population crash of water hyacinth on Lake Victoria would not have occurred in the absence of the weevils, but that it may have been hastened by stormy weather associated with the El Niño event

Tsetse control and land-use change in Lambwe valley, south-western Kenya

For a long time, trypanosomosis, spread by the tsetse fly Glossina, constrained human settlement in the Lambwe Valley, a south-western Kenya rangeland. After lengthy efforts to control tsetse over many years, the valley is currently experiencing an increase in human population growth rate, and rapid changes in land-use and cover are taking place. Using timeseries aerial photograph interpretation, social survey methods, and a review of human population trends over five decades, a three-fold expansion in cultivation in the settled areas over a 50-year period, with a consequent decrease in woody vegetation cover was identified. In the Ruma National Park, occupying a third of the valley floor, shrublands and thickets have expanded while open grasslands have decreased. The sudden increase of land under cultivation adjacent to prime agricultural land designated for wildlife conservation, exacerbated by bush encroachment and dwindling resources for tsetse control could provide a situation suitable for land-use conflicts. Sustainability of this unique rangeland is dependent on how judiciously the resources are shared among all stakeholders in the valley. This study suggests continued tsetse surveillance and agricultural intensification in the settled areas to minimise chances of conflicts in land-use

The use of sociological methods to assess land-use change: A case study of Lambwe valley, Kenya

Land-use history, not readily available for most places, remains the weakest link in nearly all studies of historic vegetation change, in Africa as well as other places in the world. Notwithstanding, communities hold a great wealth of knowledge on the processes and events influencing change on the land they occupy. The Lambwe Valley, southwestern Kenya, has a multi-ethnic population of settlers from the early 1950s. These people have seen the transformation of an initially forested area with diverse challenges to their survival, to present-day scramble for the remaining high potential land. A large part of the forces driving human settlement and consequent changes in land-use and cover is attributed to the control of tsetse and trypanosomosis. The application of a socio-economic method of mapping land-use change with the participation of the community in this study depicted trends and the underlying causes. The control of tsetse fly and therefore trypanosomosis infection was significant in driving the changes in the valley. Agricultural intensification is suggested as a means to support the resultant higher populations of people and livestoc

Grazing lands in Sub-Saharan Africa and their potential role in climate change mitigation: What we do and don't know

In 2014, the USAID project ‘Grazing lands, livestock and climate resilient mitigation in Sub-Saharan Africa’ held two workshops, hosted by the Colorado State University, which brought together experts from around the world. Two reports resulted from these workshops, one an assessment of the state of the science, and the other an inventory of related activities in the region to date.. In this short communication we summarize the main points of the first report – The state of the science (Milne and Williams, 2015). A second report is in preparation