Yes, it’s a difficult question because it’s not just about the biology – such as resilience and area relationships – in fact, it’s probably more about the socio-economic setting that will ultimately dictate how the biodiversity in any particular area fares in response to disturbance.
In the case of protected areas (that I’ll just refer to as ‘reserves’ for the remainder of this post), there’s been a lot of work done about the things that make them ‘work’ (or not) in terms of biodiversity preservation. Yes, we can measure investment, how much the community supports and is involved with the reserve, how much emphasis is put on enforcement, the types of management done within (and outside) of the reserves, et cetera, et cetera. All of these things can (and have to some extent) been correlated with indices of the fate of the biodiversity within reserves, such as rates and patterns of deforestation, the amount of illegal hunting, and the survival probability of particular taxa.
But the problem with these indices is that there are just indices – they probably do not encapsulate the overall ‘health’ of the biodiversity within a reserve (be that trends in the overall abundance of organisms, the resilience of the community as a whole to future disturbances, or the combined phylogenetic diversity of the ecosystem). This is because there are few long-term monitoring programmes of sufficient taxonomic and temporal breadth to summarise these components of complex ecosystems (i.e., ecology is complex). It’s no real surprise, and even though we should put a lot more emphasis on targeted, efficient, long-term biodiversity monitoring inside and outside of all major biodiversity reserves, the cold, hard truth of it is that we’ll never manage to get the required systems in place. Humanity just doesn’t value it enough.
That doesn’t mean, however, that we shouldn’t try to come up with better proxies. Some might recall that we did just that a few years ago when Bill Laurance organised a massive, pan-tropical survey of reserves specialists to construct an index of overall biodiversity ‘health’ within and outside of 60 tropical reserves (you can read all the gory details of the 216-author paper in Nature here, or an expurgated version in this blog post). While surveys aren’t necessarily the best ways to track biodiversity, we demonstrated that the technique is robust enough to encapsulate the required information, and it sure as hell beats no data at all.
The frightening outcome of that study is that about half of the tropical reserves we investigated had really poor biodiversity health, and that most (82%) had a declining health index over the last 20 to 30 years. Ouch! The implication is that we can’t simply build a ‘wall’ around a forest or a reef and think that it’ll be ok. No, we need to be very proactive about managing the biodiversity reserves are meant to protect via intense oversight, and avoiding any hell in a handcart outside of the reserves (e.g., deforestation, fires, poaching, road-building, etc.).
Now the Laurance et al. paper suggested a tantalising trend in the dataset – those parks that had a bigger emphasis on management seemed to do slightly better on average, which takes us back to the idea that putting more into the reserve leads to better biodiversity outcomes.
To test this further, we decided to look into the ‘management’ a little more closely. Ideally, we would have had a detailed budget and project-reporting timeline from each and every reserve in the sample, but of course that information wasn’t available to us mere mortal scientists. So we had to settle for a coarser scale of investigation – national context.
I’m happy to say that the results of that investigation have just been published in Biological Conservation, with co-authors Bill Laurance and Ian Craigie of James Cook University. Our hypothesis was simple, all other things being equal, the more a country puts emphasis on protecting its biodiversity, the better the health of the biodiversity in their reserves. The trick, of course, was to find an index of ’emphasis’ or conservation ‘commitment’.
It turns out that the IUCN has a classification system that rates reserves by their focus on biodiversity conservation: ‘Ia‘ reserves are ‘Strict Nature Reserves’, ‘Ib‘ are ‘Wildnerness Areas’, ‘II‘ are ‘National Parks’, ‘III‘ are ‘Natural Monuments or Features, ‘IV‘ are ‘Habitat/Species Management Areas’, ‘V‘ are ‘Protected Landscape/Seascapes, and ‘VI‘ are ‘Protected Areas with Sustainable Use of Natural Resources’. The first five categories are generally considered those with the highest protection value and commitment (specifically managed for biodiversity protection), whereas the last two are subject to multiple-use management. We therefore hypothesised that the proportion of protected areas in the ‘high-protection’ categories (I-IV) might explain some of the variation in protected area health, as measured by the Laurance et al. index.
The ‘all other things being equal’ component though is also pretty important, because nations differ in their overall wealth, social structure, population density and so on. We therefore compiled various other national characteristics such as economic performance, population size and governance quality (as a proxy for corruption) to control for some of those extenuating circumstances.
I won’t bother going into all the modelling details or the umpteen checks and rechecks we did to satisfy the reviewers, but the take-home message was simple – the more a country invests in IUCN Category I-IV reserves, the more its reserves in general do better for the biodiversity they’re supposed to protect. Interestingly, and confirming some of my previous work at the national scale, increasing a country’s overall wealth also reduced the biodiversity health of its reserves (another mortal wound for the environmental Kuznets curve hypothesis).
My hope is that this sort of empirical evidence will be used to justify the emplacement of more high-protection reserves, rather than defaulting to airy-faerie multiple-use zones that just don’t seem to do much to protect our dwindling biodiversity.