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Probing Population Growth Near Protected Areas
November 3, 2008 By Jason BremnerJustin Brashares and George Wittemyer’s recent article in Science, “Accelerated Human Population Growth at Protected Area Edges,” presents data showing that average population growth at the edges of protected areas in Africa and Latin America is nearly double average rural population growth in the same countries. The authors argue that this phenomenon is due to migration, as people from surrounding areas are drawn to the health-care and livelihoods programs made available to people expelled from the parks.
It’s not news that high population growth rates have implications for conservation, both in terms of land-cover change and biodiversity loss. Yet at last month’s World Conservation Congress, I heard scarcely a mention of population growth or other demographic factors. So I appreciate that the authors are urging us to look at this aspect of conservation. In addition, by studying a large number of countries and protected areas, their work helps move our thinking beyond the inherent limitations of case studies focused on a single protected area.
I feel obligated to take issue with a few of the authors’ assumptions, methods, and conclusions, however. For instance, the authors compare growth rates for individual protected areas with national rural rates, and find the former are significantly higher in the vast majority of cases. I wonder why they don’t make the comparisons with the rural population growth rates for the region in which the protected area is located, since that seems as if it would make for an even more compelling argument.
My second issue is a note of caution regarding gridded population data. The creation of a gridded population layer depends both on the size of the population data units and the way in which the population is distributed. Given the inherent inaccuracies in this process at detailed levels of analysis, how can we be sure that the populations for the 10 km “buffer areas” surrounding the protected areas are accurate? Is there any way to validate these data, and how would errors impact the authors’ analysis? This issue is particularly important because rural areas tend to have large administrative units and sparse populations.
My third issue is with the authors’ examination of infant mortality rates as a proxy for poverty. The authors analyzed poverty in an attempt to determine whether poverty-driven population growth was informing their result; they concluded it was not. Measures of infant mortality are notoriously poor at the local level, and the authors need to go further in assessing what portion of growth is due to migration and what portion due to natural increase. While such an analysis would take time, it is necessary, given higher fertility in remote rural areas.
Despite my reservations about how the authors came to their conclusion, I tend to agree that migration is driving higher population growth in areas of high biodiversity and around protected areas. The reasons for migration, however, are diverse, and my fourth issue is that I don’t think the authors provide adequate evidence to demonstrate that conservation investments are driving migration to these areas. My three main reasons for taking issue with this finding:- The number of protected areas in the world has grown rapidly over the last 40 years, and they are generally located in sparsely populated areas. During this same period, the populations of most African and Latin American countries have doubled at least once. Thus, people have migrated to new frontiers—often near protected areas—seeking available agricultural land.
- Extractive industries—including timber, mining, oil and gas, and industrial agriculture—often provide lucrative jobs near protected areas. These jobs offer migrants far greater economic benefits than the meager amounts spent on conservation. Tourism is likely the only industry than can compete with these industries in attracting migrants, and only in areas with high numbers of visitors.
- The correlations the authors found between population growth and Global Environment Facility spending and population growth and protected area staff could, as the authors note, simply mean that conservationists are wisely spending their limited dollars on the protected areas facing the greatest threats.
Jason Bremner is program director of the Population Reference Bureau’s Population, Health, and Environment Program.
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