Local and/or general?

I was lucky enough to attend the ‘Biodiversity Across The Borders’ conference in Ballarat last week. It showcased a great mix of big picture talks and detailed ecological studies. As always, student talks swept the floor, impressing everyone with their content and energy.

While sitting on a panel session, I was puzzled by a question from the floor. A member of the audience trenchantly complained that the ecological information his local group received was often ‘completely wrong and useless’. Local issues aside, the comment raised important questions about scale and specificity which, no matter how much we’d like to, researchers (and conservation planners) can never overcome.

Why do we so often get things wrong?

I appreciate that my reply to this question might sound a trifle optimistic.  However, often, I don’t think we do get it wrong; instead, information is often applied at inappropriate scales.

We can study any ecological issue from one of two perspectives: local or general. If we study a local issue in great detail, then our results will obviously be relevant to the area in question. Unfortunately our conclusions may be completely inappropriate somewhere else. Importantly, we won’t be able to predict where our conclusions will be relevant to, unless we also have broader frameworks to draw upon.

Alternatively, we can take a top-down approach and seek a broad, general understanding that is appropriate in many different contexts. This is what theoretical and conceptual development is also about. The trade-off is that general theories may not enable us to accurately predict specific outcomes in any specific place.

To give a simple example, we recently published a study on how the cover of woody vegetation has increased across Victoria in recent decades. We used remote sensing, and compared the analyses against air photos to verify their accuracy. The results turned out to be reasonably accurate when applied across many patches of vegetation. But they were very unreliable when we looked at any particular patch of bush.

How does this happen? How can a big picture view be acceptable, even if the details are inaccurate? Doesn’t the devil lie in the details?

Paradoxical as it might sound, this is normal. All generalizations ­– in ecology and life – are robust when used to discuss broad patterns, but can be spectacularly misleading when applied to specific examples. We all know that adults have bigger feet than children. However, we also know that this relationship isn’t perfect. Some kids’ hooves are truly enormous.

The same issue underlay our remote sensing study. The patterns were acceptably accurate when many patches were compared, even though many individual sites deviated from the general trend. Since we couldn’t predict which sites would deviate, we presented a big picture view only, and didn’t try to apply the findings to specific patches.

Thus, if we take a broad view, the devil isn’t in the details. Instead we create a devil of a problem when we try to apply big picture perspectives to the local scale.

Our increasing reliance on digital file transfers increases our ability to misuse information by applying it at inappropriate scales. GIS maps are only useful at the scale they were intended to be used, but it’s far too easy to grab a map layer (no matter how fine or coarse its resolution) and use it a different scale. If a vegetation map of the world is used to display patterns in a local area then, not surprisingly, the information will be senseless. But the scale is inappropriate, not the underlying information.

In ecology, scale and context are everything. We cannot transfer content without context.

So what scale should budding researchers focus on – local or general?

A fellow researcher once told me an interesting anecdote… In research planning meetings, if research users are asked whether they’d rather have: (a) detailed information that is reliable only in a local area or (b) a general perspective that is reliable over large areas, the response is invariably, “we’d prefer detailed information that is reliable everywhere”.

This makes perfect sense, but research can never deliver that. We will never have the time or resources to develop a detailed understanding of how every population, species or ecosystem operates at local scales.

Consequently, we need local and general approaches to make the best advances in conservation biology. We need to develop big-picture perspectives (theories, concepts or frameworks; call them what you will) and we also need detailed studies from local areas. Ideally, we’d marry both approaches, so that local studies directly inform our conceptual developments.

As always, in a world constrained by time and money, its all about trade-offs: we can have anything we want anywhere, but we can’t have everything we want everywhere.

There isn’t a way around this conundrum. We have to accept that many ecological studies will not provide detailed information that we can use locally. This doesn’t mean that they’re useless. Far from it, without a big picture view, we’d be swamped by contradictory local details, which we wouldn’t be able to make sense of.

Wisdom = Local + General. Not one or the other.

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