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Nothing is Natural, Everything is Natural

The downfall of traditional, REI catalog-style environmentalism is the dichotomy it posits between natural and unnatural. Real nature, we’re encouraged to think, exists somewhere else, somewhere without people, unless they’re familiar with the language of base layers or prayer wheels. We might live in the suburbs, in a patchwork of forests, but that’s not nature; and if we live in cities, all the worse.

It’s an intellectually hollow, historically myopic way of thinking. Worse than that, it’s impoverishing. Nature is everywhere; our lives are richer for recognizing and treasuring it; and unless we see it, we can’t nurture or protect it. So I was happy to stumble across an article recently published by ecologists Erle Ellis and Navin Ramankutty in a small journal called Frontiers in Ecology and the Environment. Entitled “Putting people in the map: anthropogenic biomes of the world,” it suggests an alternative system of ecological classification, one that doesn’t reflexively view human impacts as insults, but as characteristics.

Reads the abstract,

Humans have fundamentally altered global patterns of biodiversity and ecosystem processes. Surprisingly, existing systems for representing these global patterns, including biome classifications, either ignore humans altogether or simplify human influence into, at most, four categories. Here, we present the first characterization of terrestrial biomes based on global patterns of sustained, direct human interaction with ecosystems. Eighteen anthropogenic biomes were identified through empirical analysis of global population, land use, and land cover. More than 75% of Earth’s ice-free land showed evidence of alteration as a result of human residence and land use, with less than a quarter remaining as wildlands, supporting just 11% of terrestrial net primary production. Anthropogenic biomes offer a new way forward by acknowledging human influence on global ecosystems and moving us toward models and investigations of the terrestrial biosphere that integrate human and ecological systems.

What excites me about the research is the implict assumptions about the nature of nature. Ellis and Ramankutty are, understandably, more concerned with their model’s utility:

Given that anthropogenic biomes are mosaics — mixtures of settlements, agriculture, forests and other land uses and land covers — how do we proceed to a general ecological understanding of human-ecosystem interactions within and across anthropogenic biomes? Before developing a set of hypotheses and a strategy for testing them, we first summarize our current understanding of how these interactions pattern terrestrial ecosystem processes at a global scale using a simple equation:

Ecosystem processes = f(population density, land use, biota, climate, terrain, geology)

Based on our conceptual model of anthropogenic biomes, we propose some basic hypotheses concerning their utility as a model of the terrestrial biosphere. First, we hypothesize that anthropogenic biomes will differ substantially in terms of basic ecosystem processes (eg NPP, carbon emissions, reactive nitrogen; Figure 3b) and biodiversity (total, native) when measured across each biome in the field, and that these differences will be at least as great as those between the conventional biomes when observed using equivalent methods at the same spatial scale. Further, we hypothesize that these differences will be driven by differences in population density and land use between the biomes (Figure 3a), a trend already evident in the general tendency toward increasing cropped area, irrigation, and rice production with increasing population density (Figure 3c). Finally, we hypothesize that the degree to which anthropogenic biomes explain global patterns of ecosystem processes and biodiversity will increase over time, in tandem with anticipated future increases in human influence on ecosystems.

But they still can’t help but wax a little philosophical:

Anthropogenic biomes clearly show the inextricable intermingling of human and natural systems almost everywhere on Earth’s terrestrial surface, demonstrating that interactions between these systems can no longer be avoided in any substantial way. Moreover, human interactions with ecosystems mediated through the atmosphere (eg climate change) are even more pervasive and are disproportionately altering the areas least impacted by humans directly. [...]

Human influence on the terrestrial biosphere is now pervasive. While climate and geology have shaped ecosystems and evolution in the past, our work contributes to the growing body of evidence demonstrating that human forces may now outweigh these across most of Earth’s land surface today. Indeed, wildlands now constitute only a small fraction of Earth’s land. For the foreseeable future, the fate of terrestrial ecosystems and the species they support will be intertwined with human systems: most of “nature” is now embedded within anthropogenic mosaics of land use and land cover. While not intended to replace existing biome systems based on climate, terrain, and geology, we hope that wide availability of an anthropogenic biome system will encourage a richer view of human-ecosystem interactions across the terrestrial biosphere, and that this will, in turn, guide our investigation, understanding, and management of ecosystem processes and their changes at global and regional scales.

Putting people in the map: anthropogenic biomes of the world [subscription required, but email the authors and they'll probably hook you up.]

Dig their Encyclopedia of Earth entry, replete with Google Earth anthome visualization links.

And for some actual commentary, rather than scorched-earth blockquoting, grok my Wired Science co-blogger Alexis Madrigal’s take.

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