The old saying, “Fences make good neighbors” failed to take into account their environmental impact and how this ubiquitous ecosystem alteration creates winners and losers.

According to the authors of an article published in BioScience, despite the combined length of fences being greater than that of roads, they have received little attention from researchers.

"Fences have eluded systematic study for so long for good reason. Fences are both difficult to detect, and, at an even more basic level, difficult to define." Researcher Alex McInturff along with a global team explained that confusion arises from distinguishing fences from walls. In addition, because “invasive species rapidly discover and exploit breaks in fences…even where fences can be mapped, either remotely or via ground surveys, characterizing their intactness or functionality requires a closer, and often infeasible, form of evaluation."

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Despite these difficulties, the researchers were able to characterize the current state of fence research and generate a typology to guide future efforts. They learned that by restricting movement, fences profoundly affect ecosystems. Whether that is good or bad depends on the species impacted. According to the study, generalist species, those that can thrive in a variety of environmental conditions, do well and specialist species, those that thrive in a narrow range of conditions, struggle as a result of restricted access to habitats, altering community composition and changing their ecosystems.

Unintended consequences of fences are common. One fence the authors observed in their research was a conservation fence at an Australian nature reserve. Erected to protect the enclosed area, the fence disrupted the movement patterns of eastern longnecked turtles outside the fence. As a result, populations were isolated and mortality rates were high.

The authors further found the effects on non-target species have not been well studied. Their review of existing literature found that “64% (285 of 446) of the studies were focused exclusively on the effects of fencing on target species — that is, species for which a fence was built. Only 24% of the studies included both target and nontarget species, and in a mere 12% were nontargeted species studied exclusively."

The authors concluded that focus needs to increase on fence design, placement, construction and removal in order to "provide the science to manage and mitigate one of humankind's most pervasive alterations of our planet."