THIS POST IS PART OF OUR ANTHROPOCENE BIOSPHERE PROJECT–A SERIES OF POSTS ON ERLE ELLIS’ ‘ECOLOGY IN AN ANTHROPOGENIC BIOSPHERE‘ (ECOLOGICAL MONOGRAPHS, 85/3 (2015))

As a wildlife biologist I have questions about the ways Ellis’ anthroecology theory is different from the long history of ecological theory that precedes it. In reading Ellis (2015) four questions occur to me for which I could not find an easy answer. I suspect that answers might be well-documented in the literature. Nonetheless, I ask them to incite some clarity of thought for me and maybe for readers.

i. Are biological, chemical, and physical process the ultimate drivers of anthroecological theory or not?

Throughout Ellis (2015) I was conflicted between the argument that sociocultural niche construction is a unique process in which humans are the ultimate cause, and the argument that it builds on existing theory mostly from ecology, which proposes that the biological potential of habitats is the ultimate driver of these patterns.

Specifically, Ellis (2015) writes that “The evidence will show that the ultimate causes of unprecedented human transformation of the biosphere are social and cultural; not biological, chemical or physical” (p. 290). I find this statement remarkable in a couple of respects. First it seems to imply that anthroecological theory will fail if either there is a lack of evidence for social and cultural factors as the sole drivers for change, or if there is evidence that biological, chemical or physical process play any role in the transformation. This seems like a very high bar to set.

Yet, when formulating the predictions of anthroecological theory, equations 2 and 3 (p. 312) explicitly propose that sociocultural niche construction is a function of biological, chemical, and physical processes that determine suitability of biomes. Ellis and Ramankutty (2008) also indicate that ecosystem processes are a function of population density, land use, as well as biota, terrain, and geology, which seems to suggest that factors related to sociocultural niche construction are not separate from the underlying biological capacity of the landscape.

I cannot reconcile what I perceive as a conflict between the expectation, on the one hand, that sociocultural niche construction is separate from the biological and physical environment, and the predictions, on the other, that suggest that it is dependent on these factors. To me the expectation that we can separate processes that are sociocultural from those that are biological harkens to Zev’s essays on environmental under-determinism. I found a similar discussion of “having it both ways” regarding niche construction theory in Scott-Phillips et al. (2014).

ii. Is the species the correct (only) level of analysis for anthroecological theory?

I am struck that the anthroecological theory seeks to explain the difference between humans and the millions of other species on Earth. Ellis (2015) writes that “To understand why and how a single biological species gained the capacity to transform the biosphere requires an evolutionary theory of anthroecological change based on “sociocultural niche construction” (p. 290). This taxonomic focus at the species level does not seem to be a point of contention, but I wonder why this particular level of taxonomic specificity is most appropriate? If we accept the idea of the “early Anthropocene,” there were other hominids that may well have engaged in similar types of niche construction. As I read it, evidence of early niche construction in these hominid species would invalidate the theory, which declares that it is about explaining why Homo sapiens is different from all other species.

A more pragmatic concern is that most of the examples I have read do not compare changes across the global species (Homo sapiens) over time. Rather, they discuss differences among populations of Homo sapiens separated by space (or time). Yet, if the theory is about the species, then I don’t understand what the differences among human populations tell us about its validity. The niche construction literature repeatedly points to evolution of lactose tolerance in humans relative to the development of agriculture. While the inference of the particular studies is to the populations that initiated the agriculture, it is not clear to me that there is any evidence that our species became more or less tolerant of lactose as a result.

Further, the sociocultural niche construction that has altered the globe has been centered in the temperate northern hemisphere (presumably for biological, chemical, and physical reasons). However, in my opinion, evidence from human population-level studies in these regions is not sufficient to test predictions about species-level change. To my mind the predictions must also hold for indigenous and otherwise disconnected peoples, who ought to also show these changes at similar rates as those in the center of the regions of most intense niche construction. I would be interested in examples that show support for anthroecological theory at the species level.

iii. Are humans exceptional niche constructors or are they just big ones?

There is a lot of evidence that humans are niche constructors, but there is also a lot of evidence that other species are as well (Odling-Smee et al. 2003). It seems to be taken for granted that the impact of human niche construction is exceptional relative to other organisms. However, I did not find any comparative data that make that clear. There are many ecological theories that explain the distribution, abundance, impact of species using fundamental environmental drivers (temperature and moisture) and metabolic scaling relationships based in thermodynamics (metabolic theory of ecology). These theories have shown that the ultimate explanations for many ecological patterns are related to body size and the physical limitations that govern body plans (e.g., fractal geometry). Think about the social niche construction done by termites and ant colonies. Acting as single super organisms colonies can impact many hectares. And, prairie dog colonies constructed niches that covered much of the western US. In light of our body size and metabolic ecology, we’d expect human impact to be larger than other social species. But in what specific ways is the human impact exceptional—i.e. out of scale given our size?

iv. How do the predictions of anthroecological theory differ from its predecessors?

The predictions of anthroecological theory are logical, but if the question is whether humans have impacted the globe or not, the answer is obvious. I think the test for any theory is how its unique predictions are supported relative to similar preceding theories. The earliest similar general theory of which I am aware is Ehrlich and Holdren’s (1971) proposal that Ecological Impact = Population * Affluence * Technology. The United Nations Environment Program used a similar equation (UN 2002) where they equated total environmental impact to population, per capita consumption, and environmental efficiency. It seems to me that these equations would make predictions that are similar to those of anthroecological theory. Indeed, I would argue that these equations are very similar to the anthromes equations (eq. 4 in Ellis 2015, p. 312). Has there been a compilation of similar theories and their predictions to identify those that are unique to anthroecological theory?

I ask these questions not because I think they don’t have answers, but rather in to get a clearer handle on just what anthroecology theory is about—both in how it lines up with biological science, and how it represents a new step. I look forward to learning more about exactly how it brings human factors into our understanding of ecology.