Abstract
Although protected areas (PAs) are declared to provide sanctuaries for biodiversity, they are increasingly threatened by the synergistic effects of anthropic factors, invasive alien species and climate change. Consequently, interventions are required to minimize the impacts of these threats on PAs’ integrity. To inform these interventions in the South African context and under the current climate change scenario, we tested for geographic patterns of alien woody species across the network of 1,453 PAs using three alien invasion indices – alien species abundance, invaded area ratio and alien species richness. Our analysis shows that, under current climate change scenario, none of the PAs would be effective in shielding against alien plants and PAs that are geographically close tend to share similar invasion patterns. In addition, PAs that are hotspots of alien species are also geographically clustered but these findings are biome-dependent. Our outlier analysis reveals not only an island of disproportionately rich PAs in alien species, but also identifies some alien-poor PAs. We suggest that PAs that are hotspots of alien species as well as outliers of disproportionately rich PAs in alien species should be priority in monitoring and invasion control programmes in the context of the ongoing climate change.
Highlights
Protected areas (PAs) are declared to provide sanctuaries for biodiversity, they are increasingly threatened by the synergistic effects of anthropic factors, invasive alien species and climate change
Using the Global Moran’s I statistic, our analysis shows that all invasion indices are significantly clustered (Table 1), that is, protected areas (PAs) that are geographically close tend to share similar invasion indices
For example (i) we focused only on PAs that are spatially discontinuous as opposed to contiguous landscapes that consist of different land uses and (ii) the sample size of PAs was unbalanced with Nature Reserve in particular being the dominant PAs type in our dataset
Summary
Protected areas (PAs) are declared to provide sanctuaries for biodiversity, they are increasingly threatened by the synergistic effects of anthropic factors, invasive alien species and climate change. Interventions are required to minimize the impacts of these threats on PAs’ integrity To inform these interventions in the South African context and under the current climate change scenario, we tested for geographic patterns of alien woody species across the network of 1,453 PAs using three alien invasion indices – alien species abundance, invaded area ratio and alien species richness. A recent study identified localized hotspots and coldspots of seagrass in eastern Canada[27] Such analysis demonstrates the simplest form of invasion area mapping by focusing on a single species. It is the most comprehensive study in the country’s PAs that are affected by many invasive species[15,32,33]
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