By Joern Fischer
I just read the recent paper by J. Franklin Egan and David A. Mortensen in Ecological Applications, on land sparing versus land sharing. I liked the paper in that it implicitly raised the issue of scale.
Funnily enough, the authors conceptualise the issue of land sparing versus land sharing carefully, but still, come to a different conclusion from the one I would have reached; or rather, despite being explicit about scale, I am not sure that a firm conclusion is possible regarding land sparing versus land sharing. Let me explain…
Egan and Mortensen conclude that in agriculturally dominated landscapes, field margins and other non-cropped areas may hold more biodiversity than vast areas of agricultural fields; hence even small set-aside areas like field margins would be better than vast fields that are biodiversity-friendly. This is because increases in within-field biodiversity are relatively small, whereas just a small margin (for example) can hold lots of extra species. This makes good intuitive sense, and is supported by their data.
But what’s the conclusion? That land sparing is better, or that land sharing is better?
Egan and Mortensen conclude that this situation suggests that land sparing is better — sparing some margins (for example) is better than sharing crops and other elements within fields. To me, I’m less sure … if there are biodiverse field margins criss-crossing a landscape, isn’t that a landscape actually one of land sharing? What exactly is the difference between land sparing and land sharing?
The point here is that current debates have mixed up issues of scale and issues of mechanism. To me, a typical land sparing situation is about large nature reserves set aside to offset intensive land use elsewhere. But to Egan and Mortensen, even small field margins are a land sparing strategy…. while to me, that kind of “feels like” land sharing. We go through the same conceptualisations, but our language and definitions are different, and so we may never agree … unless we resolve such inconsistencies in the literature.
The current debate may be mixing up two things: the mechanism (setting something aside or not) versus the scale (big or small protected areas)? What I argued in 2008 was that in fact, land sparing and land sharing are much the same thing — but at an increasingly fine spatial scale, we tend to see a landscape as land sharing, whereas at coarse scales, we see it as land sparing. At an extremely fine scale, for example, biodiversity elements are directly included in fields; at a slightly larger scale, we might talk about protecting field margins; at a really large scale, we might talk about big protected areas set aside as national parks.
Notably — at least this is what I argued in the past — this happens along a continuum. Land sparing and land sharing are not actually different in principle. They are both about integrating conservation and production, with the key difference being at which scale.
Why does this matter right now? Because at the moment, the literature is mixing up the mechanism (setting aside land = land sparing) and the scale. I argue that setting land aside at fine scales is in fact land sharing. And moreover, there is not distinct point at which land sparing turns into land sharing… this happens along a continuum of scales.
So what does this mean for the dichotomy currently causing lots of papers? Frankly, I think it’s a conceptual dead-end. A better question would be at which scale should we integrate conservation and production, given particular socio-economic contexts. To me, that would be a question worth asking. But will there be a globally definite answer to this — i.e. put cynically, will this yield papers in Nature and Science? I predict not.