Science in the city
Cities are ecosystems with high levels of biodiversity and often include relics of natural and semi-natural habitats. They also contain a wide variety of uniquely urban habitats (brownfield sites, gardens, parks and industrial areas, for example) and are centres of importation, naturalisation and the spread of non-native species.
Globally, more people now live in urban areas than rural, and for many people, urban biodiversity is the only biodiversity they experience during their lives. Urbanisation is increasing around the world and as this trend is set to continue, understanding and protecting urban wildlife and connecting people with the urban biodiversity around them is of paramount importance. Good urban ecological stewardship is critical to global sustainability.
The Earthwatch project New York City Wildlife led by Dr Cat Burns of the University of Maine is carrying out one of the first studies aiming to understand the impacts of urbanisation across different taxonomic groups in the New York metropolitan area. The project will quantify the abundance and diversity of mammal, bird, amphibian and plant communities in a range of protected areas spanning an urbanisation gradient, from extremely urban to rural.
In 2008, the project's very successful first year, sites surveyed included Central Park, New York Botanical Garden, a number of suburban parks, and pristine rural sites 40 to 50 miles from Manhattan. Teams of Earthwatch volunteers and project staff gathered data on animal and plant communities in these parks using a variety of methods specific to the sampling of each group, including mammal tracking and camera-trapping, amphibian dip-netting, pit-fall trapping and egg mass surveys, breeding bird point-surveys, and invasive and understorey plant community surveys.
Although 2008 was the first year of data collection on this project, the teams have already amassed an incredible amount of high quality data. Key results from the first year indicated that many (but not all) species of amphibians, birds and mammals are extremely sensitive to the effects of urbanisation. For example, in terms of both species richness (the number of different species) and species abundance (the numbers of individuals of each species), amphibians showed a significant negative response to increasing urbanisation (i.e. species richness and abundance were lower in the more urbanised areas).
The mammal surveys highlighted that even the most urban sites were home to populations of several common species of mammal. Larger and rarer species of mammals were recorded at the more suburban and rural sites, and black bears were camera trapped within 50 miles of Manhattan. The Earthwatch teams recorded just under 90 species of breeding birds across all of the parks surveyed and there were exciting and unexpected sightings of rarer species such as Clapper Rail, Black-throated Blue Warbler, and Cerulean Warbler.
The plant survey results indicated that invasive plant species play an important role in urban parks in the area, and showed that the abundance of invasive plants was much higher at the edges of parks than in the interior. This discovery has important management implications for parks which are long and thin and small parks, both of which have large areas of ‘edge' habitat. Moreover, it was found that plant species richness decreases with increasing distance from Manhattan, so increased urbanisation actually has a positive effect on plant species richness, possibly due to the increased numbers of non-native plant species in more urban areas.
The 2008, 2009 and 2010 teams will gather essential baseline data that will allow long-term monitoring in the future to explore the response of wildlife to increasing urbanisation over time and to help guide management of the parks.
Join the team in 2009
You can help the project team to continue to explore the intriguing trends identified in 2008 by joining the Earthwatch expedition New York City Wildlife (a full copy of the research field report from the 2008 season can be downloaded via this link). This expedition also includes teams for teenagers aged 16 to 17 and short-duration teams.
Report by Lianne Evans.