Science and the city
An Earthwatch project led by Dr Catherine Burns of WildMetro is showing the inhabitants of one of the world's largest cities, New York, that although humans created the centres of urbanisation that characterise our civilisation, we are not the only creatures to make this habitat a home.
The 4th of October every year is the United Nations World Habitat Day. This day is set aside as a time for citizens of the world to contemplate their own habitat, the towns and cities that the majority of us live in. This year's World Habitat Day falls within the International Year of Biodiversity.
Volunteers at work on the New York City Wildlife project.
Urbanisation is swiftly occurring around the world, and will continue to increase steadily in the coming decades (United Nations Population Division 2004). What is increasingly being recognised is that human health and wellbeing are linked with contact and interaction with the natural world in its many varieties.
Dr Catherine Burns says: "Though our project is still young and full results have not been realized yet, we hope that our research will impact the relationship between people and the natural environment in urban regions. The more people we can involve in this project, and the farther we can disseminate our results, the better able we will be to achieve these goals."
Over the past decade the scientific community has contributed a wealth of information on species responses to urbanisation. However, there is much variation in observed responses, and there consequently remain few hard rules for predicting the effects of urbanisation on wildlife species. In some cases, species exhibit a very strong negative response to increasing urbanisation, while other species show little or even a positive response.
Studying flora and fauna
Burns and her team, along with dedicated Earthwatch volunteers, have for the past three years conducted a comprehensive study of the flora and fauna of the New York metropolitan area along a gradient of urbanisation, from downtown Manhattan to suburban and rural areas within 100 miles of New York City. This region, though one of the most densely populated in the world, still maintains a multitude of natural, protected areas comprising nearly 25 per cent of the land area in New York's five boroughs, and considerably more in the surrounding region. The project research focuses on the mammalian, avian, amphibian and understorey plant communities due to their sensitivity to landscape disturbance, and to substantial public interest in their protection.
Working with volunteers, local citizens, scientists and park managers, the scientists are striving to further understand nature in the urban habitat to effectively protect important resources that are coming under increasing threat.
"We feel that we have made substantial progress during the early stages of this project, by involving nearly 100 participants in the field work, and by giving regular formal and informal seminars on our research and on conservation in urban regions. We anticipate that our influence in this area will increase as the project grows," says Dr Burns.
Volunteer tasks vary, with different teams allocated taxonomic group surveys according to whether the best season for surveying those species groups coincides with the time of year they are in the field. Surveys are preceded by identification and survey technique training to ensure accurate data collection and trustworthy results. The wide range of taxonomic groups surveyed illustrates just how wide a variety of species make homes within urban habitat.
Species living a city life
Three main species groups were surveyed: amphibians, birds and mammals. Across each of these three groups, common and rarer species were found across the range of parks surveyed along the urbanisation gradient.
Amphibian species found included common species such as the wood frog and spring peeper, which were found in most of the parks. The pickerel frog and the slimy salamander were found only at the more rural parks surveyed. Amphibian species richness and abundance were found to increase as the distance of the park from Manhattan increased, indicating that most amphibians respond negatively to urbanisation.
A juvenile night heron (Nycticorax nycticorax) feeds in Jamaica Bay Wildlife Refuge, New York City.
The common bird species recorded throughout the parks included the American robin, the American greenfinch and the blue jay. Rarer species included the Blackburnian warbler, black throated warbler and Cerulean warbler. Avian richness was not found to have been strongly impacted by urbanisation, but community composition (the different species making up the avian community in an area) varied substantially from park to park. Analysis revealed that much of the variation in community composition among the parks could be explained by the parks' location along the urbanisation gradient. This shows that while the number of birds in a location is not impacted by urbanisation, the types of species found in a given location are significantly shaped by how urbanised the area is.
A range of mammal species have been recorded by this project; from very small white footed mice and eastern chipmunks to the larger white tailed deer and black bear. Foxes were found within 30 miles of Manhattan, black bears within 50 miles and fisher within 100 miles. Mammal findings are important, as small mammals represent an important prey base, while the larger mammals with larger home ranges provide a good indication of the integrity of ecosystems.
Conducting amphibian surveys, volunteers employ sampling techniques that include dip-netting, pit-fall trapping (pitfall traps consist of a container buried in the ground with its rim at surface level used to trap mobile animals that fall into it), and finding and recording eggs. In 2010 bird surveys were carried out at all study sites' visual and auditory point counts (scientists and volunteers stand at a predetermined point along a transect for a predetermined amount of time and record all bird species seen or heard within that time). To monitor populations of mammals such as the white-footed mouse, volunteers set track-tubes (a small tube containing a pliable substance that any creature walking across will leave a footprint in), automatic camera-traps and interpret mammal tracks to identify which mammals are present in each area.
Setting camera traps to observe mammal movements in Blue Mountain Reserve, New York State.
Earthwatch volunteers have enabled the scientists to cover far wider areas and trap, count, measure and record a huge number of animals and plants which they would not otherwise have been able to do. Across the 2008 and 2009 study season, 91 ponds were surveyed and a total of 15 amphibian species were identified. One hundred and six bird species have been indentified and 14 mammal species have been recorded.
The accumulation of data that has been achieved for the species that share our urban habitat is vital as it gives us a new perspective on the environment in which we live. It helps to remind us that we share this space not only with each other but with a wide variety of fascinating wildlife. The theme of this year's world habitat day is ‘Better City, Better Life'. What better city than one where all the inhabitants are recognised and their place within the habitat is respected?
Earthwatch needs your help! If you would like to volunteer on an Earthwatch expedition, visit our expedition pages, or request a copy of our 2011 expedition guide, published this month.