Rapid redistribution of agricultural land alters avian richness, abundance, and functional diversity

The conversion of natural, or seminatural, habitats to agricultural land and changes in agricultural land use are significant drivers of biodiversity loss. Within the context of land-sharing versus land-sparing debates, large-scale commercial agriculture is known to be detrimental to biodiversity, but the effects of small-scale subsistence farming on biodiversity are disputed. This poses a problem for sustainable land-use management in the Global South, where approximately 30% of farmland is small-scale. Following a rapid land redistribution program in Zimbabwe, we evaluated changes in avian biodiversity by examining richness, abundance, and functional diversity. Rapid land redistribution has, in the near term, resulted in increased avian abundance in newly farmed areas containing miombo woodland and open habitat. Conversion of seminatural ranched land to small-scale farms had a negative impact on larger-bodied birds, but species richness increased, and birds in some feeding guilds maintained or increased abundance. We found evidence that land-use change caused a shift in the functional traits of the communities present. However, functional analyses may not have adequately reflected the trait filtering effect of land redistribution on large species. Whether newly farmed landscapes in Zimbabwe can deliver multiple benefits in terms of food production and habitat for biodiversity in the longer term is an open question. When managing agricultural land transitions, relying on taxonomic measures of diversity, or abundance-weighted measures of function diversity, may obscure important information. If the value of smallholder-farmed land for birds is to be maintained or improved, it will be essential to ensure that a wide array of habitat types is retained alongside efforts to reduce hunting and persecution of large bird species.