SLoSSing out climate conservation policy

There’s an old debate in the field of conservation, about what strategy is best when setting aside land for conservation. Should our efforts go into getting large contiguous areas, or would it be better to have a collection of smaller reserves distributed over a wider area: Single Large, or Several Small (SLoSS).

There are good arguments for both. A single, large area can allow for habitats that cannot occur in a smaller space. The edge of a forest, for example, lets light and wind penetrate into the understory from the side, spurring the growth of less shade-tolerant plants, different animals, and even affecting things like soil moisture. Deep forest habitats are much darker, tend to have less undergrowth, and can harbor very different kinds of life. This distinction is reliable enough, that undergraduate ecology students often do “research” on these dynamics as part of their training. It’s not generally a way to learn something new, so much as a way to practice the skills, knowing the results you should be getting. I know less about it, but I’m sure similar things exist in aquatic ecosystems, accounting for stuff like depth, fishing and other human activities, proximity to pollution sources like farms and factories, and so on.

The “Several Small” perspective is also generally about a diversity of habitats, but accounts for the way the changing landscape allows for different conditions over much wider areas. A mountaintop will have different life from a river, which will be different from a forest, or a plain, or a lake, or the boundary between those habitats. While one large place can encompass a good amount diversity in that regard, spreading your reserves out can cover more ground, so to speak. Having scattered nature reserves can also serve to create vital safe “pit stops” for migrating birds.

Both of perspectives are a form of triage, in the face of the relentless, escalating environmental destruction being driven by capitalism. The “ideal middle ground” could be described as a number of large reserves, connected by corridors, but that’s rather difficult to arrange in a world where capitalists get what they want by default most of the time.

I think this research supports my preferred approach of ending capitalism, and integrating our development into our surrounding ecosystems as much as possible (I mean, they don’t actually talk about capitalism, but in my opinion a growth-obsessed system like that can never allow for the kinds of change we need). Not only may the heat tolerance of sub-populations vary, but a population starting in a cooler area has more “room” for warming before temperatures start to get dangerous. This means that if you want a species to be able to survive global warming, the best thing you can do is make sure that the populations are not fragmented, and have space to move and change.

By conducting a metanalysis of 90 previously published studies, from which Cheng and his co-authors mined data on 61 species, the team was able to construct a set of “upper thermal limits”—specific temperatures above which each species could not survive. However, by zooming in further and looking at 305 distinct populations drawn from that pool of 61 species, they found that different populations of the same marine species often had widely different thermal limits. This suggests that some populations have evolved different abilities to tolerate high temperatures. The key then, is to keep different populations of the same species connected so that the populations that have adapted to the higher temperatures can pass this advantage on to the populations with the lower thermal limits.

In other words, imagine a wide-ranging marine species, such as the diminutive Atlantic killifish, which occurs from the warm Florida coast of the United States north to the frigid waters of Newfoundland, Canada. The northern killifish populations may be better able to withstand warming waters if some of their southern kin are able to naturally shift their range to the north.

“Scale matters,” says Matthew Sasaki, a marine biologist and evolutionary ecologist who completed this research as part of his postdoctoral fellowship at the University of Connecticut and is the paper’s lead author. “The patterns you see across species aren’t the same you see within species, and the big-picture story doesn’t necessarily match what is happening on the local level.”

In case you need the refresher, working to preserve biodiversity can help us deal with climate change. That’s why I like the idea of, to the greatest degree possible, bringing nature into our cities and other developed spaces, both by setting aside land around us for wildlife, any by making “our” territory safer. Less dependence on cars for transit (and more rail and foot traffic) would also make it a lot safer for animals to move through our landscape as they go from place to place.

When it comes down to it, they key seems to be having a clear understanding of the local conditions, and the needs of local ecosystems. What works for one place, one species, or one community of interacting species, may not work for another:

In yet another twist, the team, which was funded by the National Science Foundation and was composed of biologists specializing in terrestrial as well as marine ecosystems, discovered that this intra-species variability was primarily a feature of animals living in the ocean and intertidal areas. Populations of widespread species that live on land or in freshwater exhibit far more homogeneity in their thermal limits, and thus could be more sensitive to rising temperatures. However, on land, plants and animals can take advantage of microclimates to cool down and avoid extreme temperatures, by moving into shady spots, for example.

Taken together, the research suggests that a one-size-fits-all-species approach to conservation and management won’t work. Instead, write the authors, we need to understand how populations have adapted to their local conditions if we want to predict their vulnerability to changing conditions. A more effective approach would include ensuring that marine species can find wide swaths of undamaged habitat throughout their entire range, so that different populations of the same species can mix and pass on the adaptations that help them survive warmer waters. And on land, we need to maintain large patches of cool ecosystems—such as old-growth forests—that terrestrial species can use as refuges.

“The glimmer of hope here,” says Cheng, “is that with conservation policies tailored to individual populations, we can buy them time to adapt to the warming world.”

As with antifascist action, and human climate adaptation, local understanding, local communities, and local solutions are going to be key. The big advantage we have over more locally-focused societies of the past, is that we can retain the ability to communicate and trade globally. We really can make this world more peaceful, just, and more beautiful, all as a part of saving ourselves from the disastrous conditions we’ve created.

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