Conserving large carnivores: dollars and fence

http://onlinelibrary.wiley.com/doi/10.1111/ele.12091/abstract

Ecology Letters (2013) 16: 635–641

Conservationists often advocate for landscape approaches to wildlife management while others argue for physical separation between protected species and human communities, but direct empirical comparisons of these alternatives are scarce. We relate African lion population densities and population trends to contrasting management practices across 42 sites in 11 countries. Lion populations in fenced reserves are significantly closer to their estimated carrying capacities than unfenced populations. Whereas fenced reserves can maintain lions at 80% of their potential densities on annual management budgets of $500 km⁻², unfenced populations require budgets in excess of $2000 km⁻² to attain half their potential densities. Lions in fenced reserves are primarily limited by density dependence, but lions in unfenced reserves are highly sensitive to human population densities in surrounding communities, and unfenced populations are frequently subjected to density-independent factors. Nearly half the unfenced lion populations may decline to near extinction over the next 20–40 years.

一些自然保护者们倡导用景观的方法来进行野生动物管理，同时其他一些人则赞成在要保护的物种和人类社区直接设置物理隔离，但是直接的比较这些方法的实践还很稀少。我们分析了11个国家中42个地点非洲狮种群密度和种群变化方向与不同管理方式的相关性。发现和没有隔离的保护区内的狮群相比围起来的保护区内的狮群非常接近估计的保护区的承载能力。每平方公里每年500美元的管理费用可以在围起来的保护区内维持其承载力80％的狮群密度，但是在没有隔离的保护区达到保存其承载力一半的目标需要超过2000美元每平方公里每年。围起来的保护区内的狮子主要受到密度的控制，但是没有隔离的保护区内的狮子对于周围社区的人口密度非常敏感并且经常受到非密度因素的影响。未来20－40年内没有隔离的保护区内大约一半的狮群可能会减少到几乎灭绝的水平。