The spatiotemporal aspects of resilience in complex urban systems
Scientific disciplines have parsed the world--separating ecological systems from human systems, or political systems from environmental systems--and have given us a rich understanding of how these component parts might work. Such a partition is sometimes necessary as a way of making progress. There has been less research devoted to integrating the component parts?taking the knowledge we already have and building upon it to understand the intimate connections between ecological and human systems, and how these systems coorganize and coalesce. This union is sufficiently complex that a partition separating ecological from human is almost certain to miss crucial mechanisms and dynamics. If we are to sustain and improve the ecological basis of human welfare, and anticipate future threats and opportunities in a way that allows timely and effective action, we need an integrated analysis.
Two stories illustrate this need.
A friend of mine--a fellow ecologist--tells the tale of a northern forest, and the competition among hunting, logging, fishing, and hiking that occurred in it. Loggers wanted flourishing stands of valuable hardwoods; hunters wanted stands that would support game; hikers wanted vast tracts free of clear cuts; fishers wanted enough vegetation to reduce the flow of silt to streams. Eventually, there were attempts to reach a compromise. Economic models were used to understand contributions from forest conversion and recreation, and it was determined that the forest would contain a particular mix of species that would optimize overall utility for all forest users.
The problem? Such a forest, and forest community, didn't exist. The management plan for clear-cutting, thinning, and conservation would result not in the imagined forest, but one with a less desirable flow of ecosystem services, with fewer valuable hardwoods, reduced ranges for precious game, and an increased risk of fire. Had the stakeholders but consulted an ecologist or two from the beginning, a different imagined forest, and the crucial services delivered by it, might have become reality. As it is now, no one is satisfied.
Another friend--also a fellow ecologist--is keen on determining the largest likely cause of ecosystem degradation over the next century. He has declared that excess nitrogen from fertilizers, rather than land use clearing or global climate change, poses the biggest threat. Is he correct? Perhaps. But his extrapolations--rich in ecological knowledge basically assume that tomorrow's human behaviors will be like today's--that people will continue with detrimental activity, either oblivious to the environmental consequences, or unwilling to act to avoid them. What if, on the other hand, people are more observant and adaptable than many ecologists like to believe? Then, the understanding of the biggest threats and the actions we might take to minimize them would require, in addition to ecological knowledge, an understanding of politics, economics, and innovation. How many people and institutions must agree before a solution becomes viable? How costly is acting versus not acting? Without such an assessment, I don't know what to do with my friend's prediction. It tells me very little about the world we will face tomorrow.
Both the solution and the prediction would have been improved if the human and environmental systems had been studied together, with one influencing the other. Of particular interest in this human environment interaction is the potential for significant changes--the collapse of a civilization, the sudden conversion of blue waters to algaechoked green, the birth of the environmental movement, or the emergence of a new infectious disease. It is these significant changes, after all, be they rapid or gradual, that can most challenge our capacity to react, and thus most threaten human welfare. What do we need to understand about human environment interactions to avoid detrimental changes, and promote positive ones? Are there signals we can monitor that allow us to anticipate detrimental change, or minimize its impacts? Can we alter the ways in which we manage systems to tighten the "feedback loops", allowing more rapid response when adverse change does begin to occur?
I am currently engaged as an urban ecologist. At some point very early in this century more people will live in cities than live in rural environments. This is a fundamentally new condition for humans. Even after the emergence of agrarian societies 10,000 years ago, city living was the exception rather than the rule. Just over 10% of the world's population was urban at the turn of the last century. Cities are the most heavily modified of human environments, and their prevalence now means that environmental change in and around cities, and environmental change deriving from the flow of resources needed to maintain cities, is having an increasingly profound impact on regional and global ecological systems. City dwellers affect ecological systems. But the preponderance of city dwellers also means that an increasing number of people on the planet have their primary daily interaction with "nature" in the urban setting; be it birds and butterflies in the backyard, or shade trees in the neighborhood park, or hiking trails at the urban fringe. These daily interactions can influence attitudes towards ecological resources, ecosystem services, and open spaces. Urban ecological systems affect city dwellers.
It thus seems to me that cities are an ideal place to examine the human-environment interaction. Moreover, cities, with their diversity of citizens, allow discovery of the nuances of this interaction. How might culture, economic status, education, or ethnicity influence attitudes towards and interactions with ecological systems? How do differing values towards ecological systems influence the ways people use or manage these systems? What do those uses and management strategies mean for the long?term integrity of ecological processes, and neighborhood environments?
I am currently leading a team of researchers to examine these questions in urban neighborhood parks?the kinds that mix ballfields and picnic areas and playgrounds with trees, turf, and (in Phoenix) native desert vegetation. We are examining fifteen Phoenix parks in three different neighborhood types (high, medium, and low income, variety of cultural and ethnic characteristics). We are asking neighborhood residents what they value about their park--be it playground equipment or something more "natural" like birds or trees. We are surveying the number of people using the park, and cataloguing their activities. We are examining how the neighborhood around the park has changed over time, and what the possible concurrent changes have been in park design, management, or use. And we are analyzing how values, use, management, and history have influenced biodiversity, nutrient cycling, metals accumulation in soils, and other ecological processes.
The information we gather should tell us not only something about how ecological systems influence people, and vice versa, but should also tell us something about future trajectories for spatial patterns of ecosystem services in Phoenix. We are finding, for instance, that ecological processes in urban parks can serve as indicators for ecological processes in the larger neighborhood. If we know something about how those ecological processes depend on neighborhood history, or the socioeconomic and cultural characteristics of neighborhood residents, we can combine that information with scenarios of demographic change to determine those areas of the city most likely to experience an enhancement or degradation of ecosystem services. This information could improve management and monitoring, and ultimately improve environmental and ecological quality.
It is not enough, however, to disentangle this human/ecological interaction in one city, or at one place in time. We need to extend our understanding to other regions, and other times. I and my collaborators thus seek, in this research funded by the McDonnell Foundation, to understand certain aspects of the human/ecological interaction in two different regions; the Phoenix Basin and the Rhone Valley. We choose these two regions because there is a long history of human occupation in them, including urban occupation. There is a rich body of knowledge concerning those occupations, from the Hohokam in the Phoenix basin dating back nearly 1600 years to early agrarian societies in the Rhone Valley dating back 10,000 years. While the past may not serve as a perfect guide to the future, we do need to understand how human/ecological interactions have changed historically if we axe to anticipate how they might unfold in the future. In these two regions, and over archaeological to present-day time periods, we will address several questions concerning: (1) the time delay between environmental change and human perception of change, (2) the spatial scales over which change occurs relative to the spatial scales over which humans were monitoring change; and (3) the possible emergence of early-warning indicators of change.
Some commentators set society and nature in opposition to each other--jobs over environment, or eco-terrorism. In reality, the two are not opposed but linked. The world cannot improve human well being without sustaining the ecological basis of that well being, nor can it maintain ecological integrity if human welfare is declining. We are poised on the brink of a better understanding of the Earth's ecological systems, how humans fit into those systems, and how we can better manage and sustain them in the service of humankind.