If you've recently spent some time in a "greenspace"--an area of undeveloped landscape--you may have found that it improved your mood, reduced feelings of stress, and left you feeling more relaxed. These are only a few of the benefits of natural areas, which have also been shown to increase lifespan, reduce the length of time needed to recover from surgery, and improve cognitive abilities. Despite the growing amount of attention paid to these physical and mental effects of greenspaces, there has been little to no work investigating why natural areas have this positive impact on human visitors--until now.
(A city park--one example of an urban greenspace)
In the latest issue of the journal BioScience, an international research team (including collaborators from the University of Sheffield, the University of Copenhagen, De Montfort University, the University of Kent, the University of Tennessee--Knoxville, and the University of Exeter) describes a recent project undertaken to test the hypothesis that people respond favorably to greenspaces because of the biodiversity contained within them. The researchers focused their efforts on 34 study sites located along the 5 rivers that run through Sheffield, UK. In each location, they surveyed local bird, butterfly, and plant populations in order to measure species richness. They also interviewed visitors to the natural areas in order to gauge which site characteristics might be responsible for "psychological well-being," as reported by the visitors themselves.
(Location of Sheffield, which, with a population of 520,700, is the UK's 5th largest city)
Questionnaires explored two major sources of the potentially beneficial impact of greenspaces: their "restorative" nature, which helps visitors bounce back from mental fatigue, and their contribution to a "sense of place," deriving from individuals' emotional attachments with particular locations and the resulting importance of those places in forming a sense of identity.
As hypothesized, the well-being of greenspace visitors was positively related to the biodiversity of all three taxonomic groups. However, in an unforeseen twist, the relevant value was not actual biodiversity, as assessed by the researchers themselves, but the perceived biodiversity reported by survey respondents. Surprisingly, the relationships between well-being and actual species richness were inconsistent: While people responded positively to higher levels of avian biodiversity, they responded negatively to plant diversity and neutrally to fluctuations in butterfly numbers.
In reality, numbers of bird, butterfly, and plant species varied independently of each other across the sites. Values estimated by visitors were highly correlated, though, suggesting that greenspace users may use one set of cues to estimate the diversity of all classes of local species. The authors of the study suggest that visitors' estimates may reflect awareness of certain key environmental features--the presence of a particular charismatic species, for instance, or abundance of wildlife rather than diversity; the exact mechanism still requires clarification. Regardless, one pattern is clear: Sheffield's citizens are not very well informed about their local flora and fauna. Of all people surveyed, only 2 could correctly identify all species shown to them in a series of 12 photographs (4 each of birds, butterflies, and plants); approximately a quarter of those questioned were unable to name even one.
(A wren, Troglodytes troglodytes--one of the most common and widespread species of birds found across the 34 study sites. Blackbirds, Turdus merula, and wood-pigeons, Columba palumbus, were also frequently observed. Common plant species included bramble, Rubus fruticosus, dandelion, Taraxacum agg., and sycamore, Acer pseudoplatanus, while whites, Pieris spp., and the speckled wood, Pararge aegeria, were the most encountered butterfly species.)
Importantly (though not surprisingly), the researchers found a clear correlation between an individual's identification skills and his/her ability to accurat