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Liben Lark Heteromirafra archeri is a ‘Critically Endangered’ species threatened by the loss and degradation of grassland at the Liben Plain, southern Ethiopia, one of only two known sites for the species. We use field data from nine visits between 2007 and 2019 and satellite imagery to quantify changes over time in the species’ abundance and in the extent and quality of its habitat. We estimate that the population fell from around 279 singing males (95% CL: 182–436) in 2007 to around 51 (14–144) in 2013, after which too few birds were recorded to estimate population size. Arable cultivation first appeared on the plain in the early 1990s and by 2019 more than a third of the plain had been converted to crops. Cultivation was initially confined to the fertile black soils but from 2008 began to spread into the less fertile red soils that cover most of the plain. Liben Larks strongly avoided areas with extensive bare ground or trees and bushes, but the extent of these did not change significantly over the survey period. A plausible explanation for the species’ decline is that grassland degradation, caused before 2007 by continuous high-pressure grazing by livestock, reduced its rates of reproduction or survival to a level that could not support its previous population. Since 2015, communal kalos (grazing exclosures) have been established to generate forage and other resources in the hope of also providing breeding habitat for Liben Larks. Grass height and density within four grassland kalos in 2018 greatly exceeded that in the surrounding grassland, indicating that the plain retains the potential to recover rapidly if appropriately managed. Improvement of grassland structure through the restitution of traditional and sustainable rangeland management regimes and the reversion of cereal agriculture to grassland are urgently needed to avert the species’ extinction.
The Critically Endangered Liben Lark (formerly Sidamo Lark) is known only from the Liben Plain of southern Ethiopia, where rapid grassland deterioration is driving the species towards extinction. Fieldwork on the Liben Plain in May 2009 to assess changes in habitat and population since June 2007 recorded a significant deterioration in habitat and decline in numbers. In both 2007 and 2009, birds were associated with areas with greater than average grass cover, and in 2007 with areas of higher grass. However, between 2007 and 2009 there was a significant decline in grass cover and height, a 40% decline in number of birds recorded along repeated transects, and a contraction of 38% in the occupied area of the Liben Plain. Moreover, the cover of bare ground increased more in areas where the species was recorded in 2007 than at random points, suggesting a more rapid degradation of the best sites. There was also a loss to arable agriculture of 8% of the grassland present in 2007. Invading fennel plants increased in number and area on the plain but did not appear to influence the distribution of the lark. An analysis of NDVI showed that grassland deterioration could not be explained by drought, and the most likely explanation is that grassland quality is suffering from overgrazing. Predictive modelling suggests that, apart from a smaller and politically insecure area some 500 km to the north-east near Somalia, there is no suitable habitat for this species elsewhere in the Horn of Africa. As a matter of extreme urgency, cattle exclosures need to be established on the Liben Plain to allow grassland regeneration. This may require the ploughing of land to reduce soil compaction and re-sowing with local grass species. In the longer term, further degradation of the plain should be prevented by, for example, clearing encroaching scrub to increase grassland area and reduce grazing pressure, and by developing sustainable rangeland management practices. These actions have the full and active support of local pastoralists.
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