Keeping animals enclosed within a large-scale fenced area – even it it keeps them safe from predators or poachers or prevents the spread of disease – should be considered a last resort, according to a new report from the Wildlife Conservation Society (WCS) and the Zoological Society of London (ZSL). Even well-made and maintained fences may be broken by determined elephants as in this example from Kenya. (Photo : Lauren Evans via WCS )

Keeping animals enclosed within a large-scale fenced area - even it it keeps them safe from predators or poachers or prevents the spread of disease - should be considered a last resort, according to a new report from the Wildlife Conservation Society (WCS) and the Zoological Society of London (ZSL).

Writing in the journal Science, the WCS reviews the "pros and cons" of large-scale fencing, determining the negative consequences of fencing operations outweigh the benefits.

"In some parts of the world, fencing is part of the culture of wildlife conservation - it's assumed that all wildlife areas have to be fenced," lead study author Rosie Woodroffe of the ZSL said in a statement. "But fencing profoundly alters ecosystems, and can cause some species to disappear. We're asking that conservationists as well as other sectoral interests carefully weigh up the biodiversity costs and benefits of new and existing fences."

The study authors note that fencing a contiguous wildlife area into smaller sections results in population isolation and the potential for extinction.

"The resulting loss of predators and other larger-bodied species can affect interactions between species in ways that cause further local extinctions, a process which has been termed 'ecological meltdown,' " the WCS reported.

Additionally, the study authors contend that fences do not always achieve the goals they are intended for.

"Construction of fences to reduce human-wildlife conflict has been successful in some places but the challenges of appropriate fence design, location, construction, and maintenance mean that fences often fail to deliver the anticipated benefits," the WCS said. "Ironically, in some places, fences also provide poachers with a ready supply of wire for making snares."

Study co-author Simon Hedges of the WCS said that as an alternative to fences, wildlife managers should considers a host of other viable options before deciding to build fences.

"A variety of alternative approaches - including better animal husbandry, community-based crop-guarding, insurance schemes, and wildlife-sensitive land-use planning - can be used to mitigate conﬂicts between people and wildlife without the need for fencing," he said, noting that it has been shown that human-elephant conflict, for example, "can be dramatically reduced without using fences in countries as different as Indonesia and Tanzania."

"An increased awareness of the damage caused by fencing is leading to movements to remove fences instead of building more," said study co-author Sarah Durant of ZSL "Increasingly, fencing is seen as backwards step in conservation."