WWF, in collaboration with the Zoological Society of London (ZSL) released a report recently that has seen a lot of press coverage, including the alarming statistic that ‘over the past 40 years, there has been a more than 50% decline in the size of 10 000 representative species’ populations.’ So what does this mean for conservation in southern Africa? I’ll try and summarise the findings with my own take on African mammals.
Africa has a lot of mammals. About 1/4 (1 229 species) of the world’s ~4 700 mammal species occur in Africa, including about 960 species in sub-Saharan Africa (see http://www.eoearth.org). The Living Planet Index (LPI) as reported by ZSL/WWF is based on statistical analyses of population level time series data, for some of these species. We don’t have data for all of them, but the ZSL does their best with those data available. So what do the data say?
Sub-Saharan Africa is grouped as the ‘Afrotropical’ biogeographic realm by ZSL/WWF, and from data available for 121 African mammal populations, the ‘overall trend’ is one of decline (see Figure 1, where red = decline). Birds on the other hand seem to have increased, and there is a lot of variation around the data, for all taxonomic groups (Figure 1). Large mammals, and in particular rhino and elephant have not fared well.
There is more to the 180 page report than a documentation of decline. Here are a few aspects that I find interesting:
First, a breakdown of the ‘primary threats to LPI populations’ shows that exploitation and habitat loss comprise 81.8% of total threats! Climate change comes in at just 7.1%! Sure, additive and synergistic interactions between climate change and other threats (see10.1016/j.tree.2008.03.011) will increasingly matter, but for a while now I have thought that we are ‘taking our eye off the ball’ by worrying about climate change and not the immediate effects of human population growth (with habitat loss and exploitation being concomitant to human population growth). And human population growth continues in Africa – unabated, whereas it has slowed down elsewhere (see http://www.pewresearch.org).
Second, the positive role of Protected Areas (PA) is highlighted. Terrestrial species’ populations within PAs have declined by 18% since 1970, but this is better than the 39% decline of terrestrial populations as a whole. PAs obviously provide some refuge from exploitation and habitat loss. What really stands out though is the extent of PAs across southern Africa that have been ‘downgraded, downsized or degazetted’ (see Figure 2). More information on this process can be sourced from PADDDtracker.org, but it is alarming that over 10% of land area formally protected has been lost across central Africa. I guess though it is positive that as much as 45% of Botswana, and 42% of Namibia’s land mass is protected.
Third, and this leads on from point two, ZSL/WWF have plotted species’ ability to keep pace with climate change, estimated somewhat crudely as ‘maximum speed at which species can move (km per decade)’. Large mammals can keep ahead of change; small mammals don’t do so well. But – what will this mean if mammal spp can’t migrate out of PAs? Are PAs large enough? Is the index of ‘km per decade’ biologically relevant? And is migration alone relevant? What about plasticity? Adaptive capacity?
The real challenge – in the short term – for African conservation is to first maintain and protect PAs (and thereby populations within those PAs), and second to think very hard about how these PAs can adapt to long term climate change, in particular provision for species’ migration. The present trend toward transfrontier conservation is encouraging.
See: WWF. 2014. Living Planet Report 2014: species and spaces, people and places. [McLellan, R., Iyengar, L., Jeffries, B. and N. Oerlemans (Eds)]. WWF, Gland, Switzerland.