New research by James Robson and Fikret Berkes questions the myth that keeping people out of nature necessarily leads to gains in biodiversity and related ecosystem services. In fact, their research on indigenous cultures in Oaxaca, Mexico, supports the assumption that people can be agents of landscape renewal that allows for both cultural and biological diversity to flourish.

Traditionally, much of conservation ecology really centers around the idea that keeping people out of nature necessarily aids the provision of ecosystem services and the conservation of biodiversity. This partly stems from the fact that many ecologists i) tend to take what we would call a "neo-Malthusian" perspective on human-environment interactions - suggesting that population is the primary force through which humans impact the environment, and ii) ignore the fact that ecosystem services are essentially benefits humans derive from nature, and therefore best understood in a social-ecological context that doesn't separate the social from the ecological.

Robson and Berkes question the above assumption (that keeping people out is good for biodiversity and flows of ecosystem services), and actually quantitatively examine it by investigating the biodiversity consequences of agricultural abandonment in southern Mexico. Two communities were surveyed in Oaxaca’s Sierra Norte (northern highlands); the Zapotec of San Juan Evangelista Analco (Analco) and the Chinantec of Santiago Comaltepec (Comaltepec).

Trends of out-migration

Both communities have witnessed huge drops in their resident populations since the mid-1980s. The main reasons for this are economic and cultural (for example the fall in prices of the regions most visible cash crop, coffee) with urban centers in the U.S.A being the main destination of migrants from the region. As a result, populations in the communities are heavily skewed towards older people, there is a labour shortage and many households have turned their back to farming and cover their needs in other ways. Around 60% of farmed land has been abandoned over the past 30-40 yrs. This decline in farming activities mirrors a more general decline in livelihood activities centered around the collection of forest resources (forest-based) practice generally; household surveys showed that the time dedicated to collecting forage, firewood, timber and other forest products had dramatically decreased over the past ten years.

Effects on biodiversity

So how are these shifts in resource practices and livelihoods (remember, due to out-migration from the communities) affecting the surrounding biodiversity and the flow of goods and services from ecosystems around the communities? While the areas around the communities are seeing an increase in forest cover (forests are growing over abandoned farm fields), biodiversity was higher before out-migration began accelerating. Simply because the activities of farmers and resource users in the forests created a nice mix of habitats and forests types that really stimulated many organisms to live there. As the authors write:

"In Oaxaca’s northern highlands, however, forests have traditionally been subjected to low intensity logging and rotational (milpa) agriculture, which involve localised forest clearance to enable crop cultivation over a limited time period. Such activities had led to pronounced spatial heterogeneity in forest structure and composition, and created a forest–agricultural mosaic that comprised a complex mix of vegetation types and natural features. It is thus the close conjunction of agricultural activities as a source of disturbance, with adjacent secondary forests and old-growth forests that have contributed to high biodiversity at a landscape scale"

These findings are important in many ways. First, for policy-makers, they exemplify some of the complexities in making projections of how biodiversity trends could out play under scenarios of rural land-abandonment. In fact, this research shows how indigenous landscapes can allow for both cultural and biological diversity to flourish. Finally, the findings show that the relationship between population and the environment is neither linear nor deterministic - in other words, managing for biodiversity and ecosystem services is rarely a simple case of shutting out people and letting nature do the rest!