Human choices impact native birds and plants
We often estimate the degree of human influence on native species and ecosystems by comparing human-dominated habitats to those with few or no humans present, such as parks. However, recent research shows that human habitat modification can lead indirectly to rapid declines in native species abundance and ecosystem condition even inside parks via the effects of abundant human commensal* species, such as deer. Deer are recognized as a problematic human commensal throughout much of central and eastern North
America, where they have benefitted from an abundance of food and an absence of natural predators, but maintained their preference for palatable native species when encountered. The consequences of this interaction were made evident by Bill Alverson (U Wisconsin), who re-surveyed 115 Midwest vegetation plots established in the 1940s to find that an average of 18% of species were missing from all plots a half century later, but that a whopping 55% of species were missing from plots located inside parks. Alverson explained his
finding as a result of deer populations growing to high density in agricultural and suburban habitats absent of native predators, but finding daytime protection from harassment and hunting inside parks, where palatable natives were decimated as a consequence. Could similar processes be at work in the Georgia Basin? Five recent papers from the Faculty of Forestry’s Centre for Applied Conservation Research show compellingly that human comensals are indeed having deleterious impacts on native plant and bird populations
* Commensalism is an association between two organisms in which one benefits while the other derives no benefit or harm
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branchlines 22#1 2011