Abstract:
Land use change (LUC) is the leading cause of biodiversity loss worldwide. However, the
global understanding of LUC’s impact on biodiversity is mainly based on comparisons of
land use endpoints (habitat vs non-habitat) in forest ecosystems. Hence, it may not generalise to savannas, which are ecologically distinct from forests, as they are inherently patchy,
and disturbance adapted. Endpoint comparisons also cannot inform the management of
intermediate mosaic landscapes. We aim to address these gaps by investigating speciesand community-level responses of mammals and trees along a gradient of small scale
agricultural expansion in the miombo woodlands of northern Mozambique. Thus, the case
study represents the most common pathway of LUC and biodiversity change in the world’s
largest savanna. Tree abundance, mammal occupancy, and tree- and mammal-species richness showed a non-linear relationship with agricultural expansion (characterised by the
Land Division Index, LDI). These occurrence and diversity metrics increased at intermediate LDI (0.3 to 0.7), started decreasing beyond LDI>0.7, and underwent high levels of decline at extreme levels of agricultural expansion (LDI>0.9). Despite similarities
in species richness responses, the two taxonomic groups showed contrasting β-diversity
patterns in response to increasing LDI: increased dissimilarity among tree communities
(heterogenisation) and high similarity among mammals (homogenisation). Our analysis
along a gradient of landscape-scale land use intensifcation allows a novel understanding
of the impacts of diferent levels of land conversion, which can help guide land use and
restoration policy. Biodiversity loss in this miombo landscape was lower than would be
inferred from existing global syntheses of biodiversity-land use relations for Africa or the
tropics, probably because such syntheses take a fully converted landscape as the endpoint.
As, currently, most African savanna landscapes are a mosaic of savanna habitats and small
scale agriculture, biodiversity loss is probably lower than in current global estimates, albeit
with a trend towards further conversion. However, at extreme levels of land use change
(LDI>0.9 or<15% habitat cover) miombo biodiversity appears to be more sensitive to
LUC than inferred from the meta-analyses. To mitigate the worst efects of land use on
biodiversity, our results suggest that miombo landscapes should retain>25% habitat cover
and avoid LDI>0.75—after which species richness of both groups begin to decline. Our
fndings indicate that tree diversity may be easier to restore from natural restoration than
mammal diversity, which became spatially homogeneous.
