Human niche diversity
Theories of niche are primarily designed to analyze interactions between different species; but anthropologists are interested primarily in niche differences within a single species (Homo sapiens)
Because of cultural flexibility (and technology), humans are able to occupy extremely wide range of environments, and to adopt extremely wide range of niches Furthermore, specific human groups can become highly specialized in ways of utilizing env. (i.e., niche), and use the same env. in different ways, either sequentially, via cultural change/evolution, or simultaneously.
This has led many ecological anthropologists to argue that each human population or culture has its own distinctive niche However, different cultures are not the same as different species, since they can
1) interbreed,
2) borrow traits, or even
3) merge into single population
These possibilities make it tricky to apply ecological niche theory to analysis of interaction between diff. human populations/cultures.  However, if we keep in mind that with humans we are talking about ecological populations and not necessarily reproductively isolated ones, niche theory can be useful for analyzing processes of diversification, competition, and cooperation among human societies  In particular, it can be a useful tool for analyzing cultural/ethnic diversity
Frederick Barth's classic analysis of complex ethnic interaction in Northern Pakistan is good illustration of how niche theory can illuminate ethnic diversity.
Barth found the following three distinct ethnic groups living in river valleys and surrounding mountains. of Swat, N. Pakistan.
1) Kohistanis = seasonal agriculture + herding; oldest inhabitants
2) Pathans = sedentary agriculturalists who entered area 1000-1600 AD
3) Gujars = nomadic herders;who entered in last 400 yrs
The environment is very mountainous with 18,000 ft high peaks dissected by steep gorges in higher areas, broader alluvial valleys in lower areas.  Clearly the distribution of these 3 groups and their relations to each other cannot be described in terms of environments per se, nor can they be reduced to military/political strength (since the Pathan are clearly superior, but yet do not displace the Kohistani in the upland areas, etc.)
Complex patterns of ethnic distribution and interaction thus can be accounted for in terms of niche theory -- in particular, as results of
a) competitive exclusion; and
b) niche divergence to reduce overlap ®coexistence
Overall, the Swat example demonstrates:
1) complexity of human niche specialization
2) ability for different cultures to co-exist via niche partitioning, as if they were different "species"
3) non-compliance with the theory of environmental determinism because two or more societies can inhabit same env. (at same time or sequentially) via differences in their niche(specialized ways of utilizing environment to make living)
In recent years, ecological anthropologists and others have become very interested in the degree to which cultural diversity might interact with biological diversity, each facilitating the other.  Two important questions are:-
1) Are biodiversity & cultural diversity correlated?
2) If so, what might account for this correlation?

Are Biodiversity & Cultural Diversity Correlated?
Various recent studies examine relation between cultural & biological diversity.  Most of these studies use language diversity as a proxy for cultural diversity (e.g., the more languages native to a different area, the higher the diversity score).  It is commonplace to find some positive relationships: for example, both are highest in tropical/subtropical areas, and both are highest along coastlines
Unfortunately, the measures and scales are often crude, with the most common pattern being to
a) measure biodiversity by species richness (# of species of some type in an area, e.g., mammals),
b) measure cultural diversity by language richness (number of languages in an area), and c) tabulate both kinds of diversity at the country scale.
A slightly more sophisticated version is to focus on endemic species and languages (meaning those only found in the given area). A handful of studies measure diversity on a continuous scale (e.g., per unit area) rather than at national or regional scales. Thus, the rigorous measurement of biodiversity & cultural diversity correlation is in its infancy; unfortunately, the objects of study are going extinct at an alarming rate.

Why are Biological & Cultural Diversity Correlated?
Although the empirical evidence indicates that biodiversity & cultural diversity (or at least linguistic diversity) are correlated in their geographical abundances, this in itself doesn't tell us why this correlation occurs
Whatever the actual causal processes, there must logically fall into one or more of the following 3 relationships:
(1) Cultural diversity drives increased biodiversity
(2) Biodiversity drives increased cultural diversity
(3) Some third factor (or factors) co- determines both cultural and biological diversity
All 3 possibilities have some plausible candidates, and these are not mutually exclusive (each could predominate in particular cases)
1) Does cultural diversity enhance biodiversity?
The first hypothesis focuses on small-scale societies (locally adapted, therefore high cultural diversity per unit area)
Proposed mechanisms:
(a) Intentionally conserve biodiversity (for livelihood or for religious reasons)
(b) Create habitat mosaics & moderate disturbance regimes (burning, swidden)
(c) Low environmental impact due to low population densities & high mobility (foraging & swidden agriculture)
Evidence for (a) is mixed, while (b) and (c) are well supported
2. Does biodiversity enhance cultural diversity?
The main idea is that high biodiversity provides more niches for human populations, allowing higher cultural diversification
Evidence for this is mixed at best:
Some areas of low biodiversity have high cultural diversity  (e.g., Niger Delta), while other areas of high biological have low cultural diversity (e.g., deserts)
Biodiversity has to be “right kind” (relevant to human subsistence) to favor niche diversity (ie people don’t eat trees…)

3. Does some third factor enhance both biodiversity and cultural diversity?
There are a number of candidate “third factors”:
(a) A warmer, wetter climate = a  longer growing season ; this allows evolution/coexistence of more plant species, which in turn allows denser human populations, hence more ethno-linguistic groups per unit area (= higher cultural diversity)
(b) A warmer, wetter climate equates with more parasites.  The effect on biodiversity is as in (1), but in turn the parasites favour local cultural & genetic adaptations, and thus limit intrusion of empires & colonial populations
(c) Geographic barriers to dispersal could affect both plant/animal species & human groups.
(d) Expansion of large-scale social systems (empires, colonial powers) reduces both biological & cultural diversity.
This is arguably most important “third factor”causing correlation between biodiversity &cultural diversity, since such systems require surplus production, based on intensive agriculture (difficult in tropical forests), high population densities, and trade (hence increasing demand for extracted resources.  This of course raises the issue of the increasingly strong impacts of governmental and economic expansion ("globalization" etc.) on areas of high cultural and biological diversity in today's world.
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