Paper Of The Week: Pauli et al. 2015. The simulated effects of timber harvest on suitable habitat for Indiana and northern long-eared bats

20 May

Ecology is sometimes criticised for being an observational science rather than a truly predictive one. That is, much of what we, as ecologists, do is to try to explain existing or past patterns, rather than use our knowledge to predict what is likely to happen in the future or under different conditions. When combined with conservation, this means that ecologists are often left to implement conservation strategies reactively, after something has happened or changed, rather than pro-actively, before the change occurs in the first place. This is unfortunate as, if done properly, a pro-active approach is likely to lead to much better conservation and management outcomes than reactive ones.

However, with the advent of new statistical approaches, the availability of cheap, powerful personal computers and advances in GIS, our ability to make the types of predictions needed to test whether specific changes to the environment, especially those made by humans or those under our control, might have on specific ecosystems or species before they occur is finally within the reach of almost every ecologist. Yes, the techniques and skills might be difficult to get your head round at first, but the results are often more than worth the effort.

A great example of this is a recent paper by Pauli et al. (2015) from the journal Ecosphere titled The simulated effects of timber harvest on suitable habitat for Indiana and northern long-eared bats. Bats, like many other species, can be impacted heavily by human actions in forestry management, but what timber harvesting strategies are likely to be best for their conservation? And which are likely to be the worst?

While I’m a marine biologist at heart, this is a subject I’ve dabbled in before. This is one of the reasons I found Pauli et al.’s paper so interesting. While, in our own study, we looked at historic effects of forest management on bats, they looked at future ones, and specifically, they combined species distribution modelling and forest succession models to compare the likely impacts of nine different timber harvesting strategies on two bat species over a prolonged period of time. They also considered the differences that impacts might have on nocturnal foraging habitat and diurnal roosting habitats, an interesting extension to the more traditional approach of just looking at one, or a combination of, habitat requirements rather than looking separately at each individual component.

So what did they find? Well, you’ll have to read the paper to get the full details, but in summary, they found that the overall suitability of habitat was primarily driven by the requirements for diurnal rather than nocturnal habitats, that what might be the best strategy for one species may not necessarily be the best strategy for another, and that if you wish to have the best outcome for multiple species, you might want to select a timber harvesting strategy that was somewhere between theses two.

While these results are relatively complex and at times contradictory in terms of their impacts on the two species, they do provide concrete information that can be used to ensure that any timber-harvesting strategies are implemented in such a way as to have the best outcome possible for all species being considered, and that is something that is always better to know before you implement them, rather than afterwards.

Of course, as with any predictions which you’re going to use for setting conservation or management strategies, you have to ensure that your predictions are accurately, but as long as you have the appropriate spatial and temporal validation as part of the investigation process, this issue can often be easily avoided. Then all that’s left is to say: welcome to the world of predictive ecology.

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Dr Colin D. MacLeod,
Founder, GIS In Ecology
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