Urbanization is defined as a continuously expanding urban area or core municipality . Urbanization is becoming increasingly prevalent as the human population grows. This is the main cause for habitat loss and fragmentation, two driving forces in the current extinction rate, which is 1000 times that of the historical rates . Species capable of living in the urban environment tend to exhibit specific characteristics. These characteristics include high thresholds for fear (cortisone levels), short flight distance, high reproductive rates, capability of maintaining high densities (of the same species), and species adapted to high disturbance and/or edges . Animals without these characteristics (and plants without the last three) are unlikely to thrive in urban development . Over time this may cause a homogeneous landscape where plant and animal species are increasingly more alike and species that cannot survive in these areas to go extinct [3,4].
In a recent study conducted in Southern Australia, Isaac and colleagues used habitat selection to examine the behavioral responses of 6 arboreal marsupial species in Australia to increasing levels of urbanization . There were three similar sized areas used in the study, a highly developed area with mostly impervious surfaces, an urban fringe area with a mix of impervious and other land cover, and a completely tree covered area . Throughout the experiment, each marsupial species selected different habitats based on their development level splitting into three groups across the landscape: a disturbance-intolerant group (3 species), a moderate tolerance group (1 species), and a disturbance tolerant group (2 species) . Therefore the potential for habitat to be suitable for these marsupials was significantly based on the urbanization gradient .
This study gives hope for the future of biodiversity, as it can be applied to urban development everywhere. It will be virtually impossible to stop urbanization from occurring more frequently, however people can build a civilization that is more integrated with the native environment. By creating this urban gradient some species diversity can be sustained. However, a critical piece to this is a need for ample area in the urban fringe and forest cover environments like in the marsupial study discussed above . If the urban areas continue to expand, then the urban fringe section for the moderate tolerance group and the forest cover patch for the disturbance-intolerant group can get too small to sustain populations .
Now is a time when human development choices can forever alter life on earth. Instead of thinking of humans as a separate entity from nature why not think of them as interconnected? Debating whether something is “natural” due to amount of human influence may be irrelevant to present and future biodiversity . Humans have been altering ecosystems for centuries and some of those changes are positive. For instance, pre-Columbian indigenous people in the Amazonian rainforest would compost to create sustainable forest gardens . These ancient gardens continue to show a positive ecological footprint as Amazonian Dark Earth (ADE) which is one of the only soils rich in carbon found in these forests today . Given the marsupial study, it is possible that present day animals have an ability to coexist with humans based on an urban gradient. This would mean that human disturbance like urbanization is capable of maintaining biodiversity if it is conducted in a sustainable way.
– Savannah Maynard
- Carolan, Michael S. “Greenhouse Gases: Warmer Isn’t Better.” Society and the Environment: Pragmatic Solutions to Ecological Issues. Boulder: Westview, 2013. 15-39. Print
- Isaac, Bronwyn et al. “Simplification Of Arboreal Marsupial Assemblages In Response To Increasing Urbanization.” Plos ONE 9.3 (2014): 1-15. Academic Search Premier. Web. 3 Mar. 2015.