The lowlands of the Cape Floristic Region (CFR) have long been recognized as priority areas for the conservation of biodiversity due to their extreme richness and the major reduction in extent from severe transformation of the landscape. Unfortunately the remnants face many additional threats. Climate change is expected to be a major driver of change over the coming decades, but its interaction with landscape transformation is likely to be truly devastating. For instance, the spatial distribution of an ecosystem’s climatic envelope may shift or be reduced by climate change, but, this can be greatly exacerbated by loss of available habitat to landscape transformation. Furthermore, fragmented habitats that are isolated within an unsuitable matrix constrain species’ abilities to track shifting climates. The objective of this study was to quantify the threat of climate change for CFR lowland vegetation fragments, and the extent to which landscape transformation and fragmentation have exacerbated this threat. We quantified climate space, climatic stability (i.e. overlap between historic and future climate space) and climate velocity in both natural and transformed landscapes, and compared these to historic climate trends (1950–2000). This allowed us to determine the independent and interactive effects of both climate change and landscape transformation.
Results/Conclusions
Climate change in the region is expected to reduce the geographic extent of climate space available to lowland Cape fragments. However, our analyses indicate that landscape transformation drastically reduces the geographic extent of climate space, irrespective of climate change. Additionally, landscape transformation further reduces climatic heterogeneity. Similarly, climate stability was found to be low, and further reduced in transformed landscapes, indicating potential climatic extinction in highly transformed regions. Climate velocities in the region were found to be high, exceeding the average dispersal range (km/y) of characteristic ecosystem biota, while fragmentation increases the distance to analogous habitats, further limiting the ability of biota to track these fast, shifting climates. These findings show that landscape structure amplifies the anticipated climatic changes in the region. Though much conservation emphasis has been placed on habitat loss and the protection of remnant ecosystems, it is important to consider the interaction between landscape transformation and climate change.