Get reliable science

In the Sahel and the Kalahari, the growth in groundwater extraction via simple wells and boreholes is contributing to an increased use of dryland natural resources, to competition for resources, and to environmental changes. Livestock production systems in particular have expanded through the utilisation of groundwater in areas devoid of perennial surface water sources. Environmental changes are most marked in vegetation systems that were utilised ephemerally and opportunistically in years of good rains prior to the all-year-round exploitation facilitated by groundwater. The nature of vegetation changes, notably biodiversity reduction and changed relationships between annual and perennial grasses and bush cover, is considered, including whether such changes represent environmental degradation and whether they are permanent. Process studies indicate that bush encroachment, a particularly marked form of vegetation change, is reversible at decadal to century time-scales, in the context of the natural dynamism of dryland ecosystems. At shorter time-scales such changes can even open up new resource opportunities that may relieve pressures on critical grazing resources at times of environmental stress. Ultimately however, available data on water availability suggest that the rate of groundwater extraction is probably unsustainable, and this may provide the ultimate limit on the wider environmental impacts that borehole-centred livestock systems have on the environment.