Urban Areas Have Ecological Integrity(3-8)

Can urban areas have ecological integrity? Reed F. Noss INTRODUCTION The question of whether urban areas can offer a habitat and wildlife within and around urban areas, semblance of the natural world – a vestige (at least) where most people live. But, if we embark on this of ecological integrity – is an important one to many venture, how do we know if we are succeeding? people who live in these areas. As more and more of There are both social and biological measures of the world becomes urbanized, this question becomes success. The social measures include increased highly relevant to the broader mission of maintain- awareness of and appreciation for native wildlife ing the Earth’s biological diversity. and healthy ecosystems. The biological measures are Most people, especially when young, are attracted the subject of my talk this morning; I will focus on to the natural world and living things, Ed Wilson adaptation of the ecological integrity concept to called this attraction “biophilia.” And entire books urban and suburban areas and the role of connectiv- have been written about it – one, for example, by ity (i.e. wildlife corridors) in promoting ecological Steve Kellert, who also appears in this morning’s integrity. program. Personally, I share Wilson’s speculation that biophilia has a genetic basis. Some people are Urban Ecological Integrity biophilic than others. This tendency is very likely Ecological integrity is what we might call an heritable, although it certainly is influenced by the “umbrella concept,” embracing all that is good and environment, particularly by early experiences. My right in ecosystems. It encompasses other conserva- own experience, which includes working many tion values, including biodiversity, ecological years as a camp counselor and environmental resilience, and naturalness. The first reference to educator early in my career, and having 3 children of integrity in the environmental literature was Aldo my own, suggests that most children are biophilic. Leopold’s famous statement in his essay on land They are fascinated by non-human life forms. Kids ethics: “A thing is right when it tends to preserve the that have abundant exposure to nature tend to be integrity, stability, and beauty of the biotic commu- more biophilic. As they get older, however, most nity. It is wrong when it tends otherwise.” Many kids seem to lose touch with nature. They are years later ecological integrity (specifically, chemical, socially conditioned to value television, computers, physical, and biological integrity) became a goal of and video games above bugs and salamanders. the U.S. Clean Water Act (1972), the bilateral Great Their teachers and parents reinforce whatever fears Lakes Water Quality Agreement (1978), and other they have about the outdoors (e.g. about snakes, environmental policies in the U.S. and Canada. The spiders, and poison oak) and their peers tell them development of ways to actually measure ecological that nature isn’t “cool. Only nerds are interested in integrity came later. Such measurements have been that stuff.” With few or no natural areas near their applied mostly to aquatic ecosystems. Most note- homes to offer alternative experiences, many young worthy is Jim Karr’s index of biotic integrity (the people let their biophilia dwindle away to nothing as IBI). they grow older. It is no wonder we have a populace The IBI is based on the idea that the biotic integrity distanced from nature and unwilling to support of an aquatic ecosystem is affected by 5 classes of meaningful conservation programs. environmental factors: water quality, habitat struc- I have just outlined what I believe is the major ture, energy source, flow regime, and biotic interac- challenge of urban wildlife conservation. What, then, tions. The IBI assumes that fish (or other taxa, such do we do about it? Basically, what we do is maintain as benthic invertebrate) communities tell us much and, where possible, restore a lot more natural more about integrity than chemical measures because Author’s address: Biology Dept., University of Central Florida, Orlando, FL 32815 Proceedings 4th International Urban Wildlife Symposium. Shaw et al., Eds. 2004 3 biotic communities tell us much more about integrity We might justifiably ask if it is even possible for than chemical measures because biotic communities urban landscapes to have ecological integrity. Ecologi- integrate the effects of numerous environmental cal integrity is typically measured with respect to factors. Generally, as human disturbance increases, some undisturbed reference condition. As defined by total species richness, number of intolerant species, Karr, the IBI value for a site is a measure of the and number of trophic specialists decline, while the deviation of the biological community at that site from number of trophic generalists increases. a baseline condition that represents “a biota that is the Attempts to develop terrestrial indices of ecological product of evolutionary and biogeographic processes integrity, or indices for entire landscapes including in the relative absence of the effect of modern human terrestrial and aquatic components, have been less activity.” Although I do not wish to dilute the concept successful. Nevertheless, a number of potential of ecological integrity, I suggest that reference sites in indicators and indices are emerging. One attempt to urban landscapes might be a bit different from those in develop a terrestrial IBI is in progress at the U.S. wildlands. We cannot expect an urban landscape to Department of Energy’s Hanford Nuclear Reservation meet the same standards for ecological integrity as in Washington. This work, by Jim Karr and colleagues, rural or wildland areas. Instead, we might establish a is examining species, taxa, and ecological groups of gradient of reference sites corresponding to the invertebrates and plants in the shrub steppe to deter- gradient in naturalness from urban areas to wildlands. mine their utility as indicators of human disturbance. The reference site for an urban landscape in a particu- Among the preliminary results, are that species lar biogeographic region would represent the best richness of invertebrates and native forbs declines in possible condition that an urban landscape in that response to increasing disturbance, as does shrub region might achieve. “Best possible,” in turn, would density and cover. On the other hand, exotic annual be defined according to degree of similarity to refer- plant taxa and density increase with disturbance. ence sites in wildland landscapes in the same region. Other examples of potential indices of ecological Thus, we recognize that although urban areas will integrity that are promising but not yet well tested never have the biodiversity, naturalness, and ecologi- include a multi-metric assessment of the conservation cal resilience of pristine wilderness areas, there are value of redwood forest landscapes developed by Jim reasonable standards they can meet. Nevertheless, Strittholt and me, and a broad assessment of the meeting those standards will require significant ecological integrity of the Interior Columbia Basin changes in habitat apportionment and management in undertaken by the USDA Forest Service and cooperat- our cities and suburbs. ing agencies. In the latter study, each of the 164 sub- The question of how one might measure ecological basins were rated as having high, medium, or low integrity in urban landscapes is beyond my scope in ecological integrity for a maximum of 5 components: this paper. I believe an adequate index would consider forestlands, rangelands, forestland hydrology, range- the composition, structure, and function of the urban land hydrology, and aquatic systems. ecosystem. An initial list of indicators should probably No study, to my knowledge, has investigated the include representatives of all these groups, ideally at ecological integrity of entire urban landscapes. several levels of organization. On the other hand, the However, biotic integrity has been evaluated in urban interdependence of composition, structure, and stream segments, for example with respect to riparian function suggests that indicators in one group might vegetation. In the Toronto area, a threshold of degra- be surrogates for the others. We might, for instance, dation of streams was reached under conditions get a good handle on the structure and function ranging from 75% removal of riparian vegetation in simply by monitoring the biota (i.e. composition). areas with no urbanization to 0% removal of riparian Conversely, it might be faster and cheaper to measure vegetation in areas with 55% urbanization. Ongoing habitat structure directly, especially at the landscape work in the Georgia Piedmont is showing lowest IBI scale where remote sensing and geographic informa- scores for streams in urban areas with the greatest tion system (GIS) technology permits rapid, quantita- amount of impervious surface from commercial, tive measurements. industrial, and transportation land uses. In this study Importantly, indicators of one attribute can be used correlations between IBI scores and percent forest to test and validate the others. For example, the only cover within 50 m of streams or whole watersheds are way we will know if indices of habitat structure or similar; suggesting that restoration of urban water- landscape pattern correspond to ecological integrity is sheds should consider land-use and land-cover of the by measuring responses of the biota to changes or whole watershed,

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