It is impossible to preserve biodiversity without considering the role of urban sprawl, as is illustrated by recent studies examining the relationship between urbanization and biodiversty. Several suggestions have been proposed for how best to protect biodiversity in and around cities. One suggestion is that developers set aside conservation areas within their projects in order to protect natural vegetation, which is often completely destroyed by developments (McKinney, 2002). The benefit of this type of solution is that the preserved biodiversity also becomes a part of the new construction. Thus, the owner of the development has a personal investment in the preserved area. Others propose that the problem of urbanization be approached from an economic standpoint.
One paper sums up the problem as follows: “The list of endangered species is growing because the scale of the integrated economy, and therefore the causal network of species endangerment, is increasing” (Czech et al., 2000). That is, economic drivers are also major causes of biodiversity loss (Czech et al., 2000). It is also important to note that the transition to an “information economy,” which one might expect to have fewer industrial polluters, is not expected to have any less of an effect on biodiversity than the industrial model (Czech et al., 2000). Therefore, any solution for reducing human effects on biodiversity lossi n urban areas must consider economics.
To maximize the effects of new policies, governments should implement them at the local level, ideally at the city level itself. But state, national, and international bodies also have a role to play in our solution. Ideally, these government levels will institute regulations that support the policies passed by local governments. Representatives from the International Committee on Biodiversity should work closely with the local governments to determine what specific areas of the cities are causing the most damage to biodiversity. However, for these areas to be identified there must be some consistent measurement system.
The Wildland-Urban Interface can be used to determine the potential that an area has to affect local biodiversity (Radeloff, et al., 2005). This interface uses local housing density to quantify how much of an impact humans have on the environment (Radeloff, et al., 2005). It was developed by the U.S. government and is currently used to analyze the risk of fire to cities that border wilderness areas in the western U.S. There are two different WUI types: intermix and interface. Interface WUI describes land that abuts wilderness areas while intermix WUI describes housing that is within a wilderness area, where wilderness areas are defined as those that contain over 50 percent wild vegetation (Radeloff, et al., 2005). The current definition of WUI encompasses areas that have a 6.17 house-to-square-kilometer ratio (Radeloff, et al., 2005). Interface WUI also requires a boundary to be set between the urban and wilderness areas. The main purpose of the WUI is to quickly and systematically identify the urban areas of the world that have direct interaction with wilderness areas.
Since there is a strong correlation between urban density and biodiversity loss, as shown by Pillsbury & Miller as well as by Czech, the WUI can provide information about the potential impact of an urban area on biodiversity. However, the interface itself does not take into account the loss of biodiversity or wildlife. It computes the ratio of housing density to area and then compares that value to the minimum value required for classification as interface or intermix WUI.
However, this ratio can be used to set standards for what constitutes a high-impact area with regards to biodiversity. These standards would ideally be created by an international committee, such as the International Committee on Biodiversity (ICB), but could also come from national governments. The minimum density required for an area to qualify as WUI will be determined by this committee or governments, as will the boundary area that determines how far from the wilderness the interface WUI extends. In addition, implementation costs should be low, since governments currently use this interface, the data required for its computation are readily available, and the standards for its application are well defined.
Once high-impact areas have been identified, policies can be enacted to mitigate the effects that humans have on biodiversity, some of which are listed in Figure 3. Policies will be formulated to reduce the harm done by these activities, such as reducing the amount of land to which tourists have access and promoting more sustainable housing development projects.
In addition, policies to stop the expansion of cities will be enacted. Since housing density has been correlated with biodiversity loss, the world's total urban area should not continue to expand. The amount of the Earth’s surface covered by interface and intermix WUI cannot be allowed to grow either. If the expansion of cities is allowed to continue unchecked, the amount of wilderness directly impacted by urban areas will increase. Thus, the ICB must determine the minimum housing density for interface and intermix WUI, classify the entire area of the world by WUI type, and write regulations to prevent the amount of land covered by WUI in the world from increasing in order to protect biodiversity from human urban areas.