.| Baltimore Ecosystem Study
| Sustainable Baltimore: Myth or Reality | ||||||
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Steward T.A. Pickett What is Sustainability? The idea of sustainability is a powerful one. But because there are so many ways to think about it, confusion and uncertainty are sometimes associated with it. As an ecologist, I think that ecological perspectives of sustainability are useful in clearing things up. In part, this is because the sustainability of all societies is based on the sustainability of complex interactions between living things and the physical world. In other words, we all depend on the sustainability of ecosystems (Figure 1).
Ecological sustainability is associated with several important capacities of ecological systems. First is the fact of persistence. Ecological systems have long histories, and continue to exist in all places where the physiological needs and limits of organisms are satisfied. The systems change as new species evolve or slowly migrate into them, or as the environmental conditions change around them. However, persistence is only an indicator that systems are sustainable. How is persistence achieved? That brings up the second aspect of sustainability – resilience. Ecosystem resilience allows a biological system to bend with bumps and stresses, rather than break. The numbers or kinds of species shift, the rates and predominance of different ecological processes change in the functional mix of what goes on in a system. But the system as a whole rolls with the punches. This kind of resilience depends fundamentally on the adaptability of organisms. Adaptability is the result of organisms’ genetic capacity to generate offspring that can take advantage of shifted conditions, or of the genetically determined broad physiological tolerances of some organisms. The adaptability of the component organisms is thus key to the sustainability of ecosystems. A final aspect of sustainability is the openness of ecological systems. A local system does not necessarily have to have all the tools for sustainability in place. Additional resources or new organisms can sometimes become available locally and fill a functional gap in an ecosystem created by some stress or disturbance. Many systems depend on this kind of openness. For example, a lightning strike in a forest may kill one or a few trees. But other trees that can handle the new conditions migrate in, or perhaps germinate from buried seeds, to literally fill the opening. The new occupants prevent loss of some of the resources, prevent soil erosion, and at the same time, find conditions they need that were not present beneath the closed forest canopy that existed there before.
Ecological sustainability is fundamental – it is the foundation – for our human enterprise. But when we ask about sustainability in the context of human activities, two additional aspects of sustainability must be included in our thinking. These two are social sustainability and economic sustainability (Figure 2). Social institutions, communities, social norms, and education are all involved in social sustainability. These social features are the ways in which people organize and respond to satisfy their material and psychological needs. Economic sustainability refers specifically to the ability to derive a livelihood and to have the financial resources to participate as individuals, households, and institutions in the work of society. These three features of sustainability – ecological, social, and economic – are often called the triple bottom line of sustainability. All three have to be in place for a ecological-social system to be resilient and adaptive, and hence to persist through internal and external changes. There are countless examples of frontier towns, ancient civilizations, ways of life, and economic enterprises that were not sustainable. Once we move beyond strictly biological ecosystems, failure to be sustainable is commonplace. Human Ecosystems We inhabit the Earth through inserting ourselves in biological ecosystems, and by building new, hybrid kinds of ecosystems. These new ecosystems, which have become the norm as human population has grown to 6.6 billion people, can be called human ecosystems. The basic concept of the ecosystem, invented for ecological research in places where people were not in residence, or had relatively modest effect on the habitat, was that such systems were composed of organisms and the physical environment with which they interacted. Plants, animals, and microbes on the one side of the equation, and air, soil, water, temperature, light on the other side. When these components interact in a place, they constitute an ecosystem. Ecosystems now have human company for the biological organisms and engineered, built, or artificial features joining the physical environments. So human ecosystems have new components and new interactions (Figure 3).
In a way, human ecosystems are more complex than natural ecosystems because human decision making and human artifacts have many additional effects, some of which are hard to see right away. People do many things in ecosystems that have indirect or unintentional effects. It is easy in human ecosystems to forget the strictly ecological components and the biologically mediated processes. Yet there is increasing evidence from the young science of urban ecology that the biological processes in city and suburban ecosystems can be substantial. For example, in metropolitan Baltimore, quantifying how nitrogen moves through the system has documented that even suburban portions of the landscape can retain substantial amounts of the nitrogen that comes in as pollution from the atmosphere or from fertilizer. This is an important finding because it suggests a tool for helping manage nitrogen leakage into the streams that ultimately feed the Chesapeake Bay. Reducing nitrate, a particularly polluting form of nitrogen, in the Bay is a regulatory mandate aimed at improving water quality and the health of aquatic organisms and fisheries that depend on the Bay. A second example of a biological process in the human ecosystem of metropolitan Baltimore is the flow of carbon through the system. Carbon is the main building block of the living world, and so it is important to keep track of it. However, carbon in the form of carbon dioxide, contributes to global warming. Carbon dioxide in the atmosphere continues to increase as a result of the burning of fossil fuels – coal and oil – in industry, transportation, and the generation of power and heat. Carbon dioxide is a powerful reflector of the heat that the Earth radiates toward space. As the carbon dioxide content of the atmosphere has increased, along with some other human generated “greenhouse gasses,” the temperature of the Earth has increased because more radiant heat has been trapped. There is great need to avoid some of the effects of global warming by reducing the amount of carbon dioxide in the atmosphere. A question about urban ecosystems concerns their net contribution of carbon dioxide the atmosphere. In metropolitan Baltimore, we have discovered that suburban-style neighborhoods containing trees and lawns in fact have some absorptive capacity for carbon dioxide. The plants that grow in these areas absorb more carbon dioxide than expected, making these neighborhoods less a source of carbon dioxide to the atmosphere than originally thought. Of course, they are not yet net sinks or storage spots for carbon, but their biological activity means that it will take less work to reduce urban carbon contribution than at first thought. The biological part of the ecosystem is producing an important benefit or service. Watersheds and Ecological Functioning As a scientist, I take the watershed idea for granted. It is such a common and widely shared tool in ecology, that its importance almost goes unremarked. However, its power is rarely used in public decision making because this idea is not much appreciated by most people. A watershed is, simply, an area that drains into a single point. Watersheds are defined by drainage (Figure 4).
Sometimes the idea is also labeled a catchment or a basin. In moist climates, such as the Eastern United States, watersheds end when the stream empties into another stream, thus starting a different watershed, or when a stream empties into a lake or the ocean. Watersheds can be small, as for example my back yard which has a central low spot, and collects water from a couple of adjoining lots. When the rain is hard and fast, or falls on frozen ground, there is standing water in the middle of my backyard watershed, which drains to ground water. Or a watershed may be huge, as in the case of the Mississippi River drainage, which encompasses about a third of the conterminous United States. In the middle are a whole range of watersheds, such as the three watersheds that are shared by Baltimore County and Baltimore City. Each is defined by a stream that drains it – Gwynns Falls, Jones Falls, and the Herring Run/Back River. A smaller catchment also drains directly in Baltimore Harbor. The Gwynns Falls, with which I am most familiar, is roughly 17,150 square kilometers (6,622 sq miles) in extent. The watershed idea is powerful because the water moving through them does a lot of work. Erosion and the transport of sediment and dissolved materials take place in watersheds. Streams do much biological work as well, at least when they contain habitat for organisms and traps for natural organic matter. Nutrients are retained in the streams draining watersheds, and some of the polluting forms, such as nitrate, can be converted to a gas and released to the atmosphere rather than contributing to the pollution load of the Bay. Finally, watersheds are important because the land and water within them are integrated. Water flows over the land surface and in the ground water, leaching nutrients and contaminants. Materials in the water interact with vegetation and soils. The strips of vegetation near larger streams – called riparian zones or buffers – are hotspots of biological activity and nutrient processing. These many functions and effects of watersheds, plus the fact that they are sensitive to human actions and decisions affecting the lands that are the source of the materials – trash, nutrient pollution, biotic contamination, and so on – means that watersheds must be better appreciated by the public. Watersheds are not small buildings near a lake, or an outbuilding where you store your bottled water. They are, rather, important and integrating components of the human ecosystem. Perhaps one of the most important features of watersheds it the fact that they do not respect human boundaries. The city-county boundary that intersects the Gwynns Falls, Jones Falls, and Gunpowder watersheds does not stop the flow and the transport of materials downstream. The integrative power of these watersheds does not balk at the boundary. Understanding and managing the watersheds requires knowing how the whole watershed works, not just the county part or the city part. Watershed Sustainability Putting the important ideas of watershed and sustainability together points to the significance of the Baltimore Watershed Agreement, signed by the City of Baltimore and Baltimore County in 2006. What is needed, from an ecological perspective, for watershed sustainability? First, we must adopt an ecosystem view of watersheds, and recognize the human benefits that derive from the biological work that watershed ecosystems do for free. In fact, finding ways to allow the biological component of ecosystems in urban watersheds to do more work of regulating water quality, reducing water flow, and reducing pollution are excellent opportunities. This is the essence of enhancing sustainability in urban and other human ecosystems: recognize the biological components and increase their ability to do more free work. Once the ecological components and their functions toward sustainability are recognized, there still remains much scientific research required to document the actual amounts of work done. Research to assess how development, redevelopment, plans, and engineering projects actually affect ecological function is also much needed. This kind of ecological study is still quite rare, but there is an increasing body of knowledge to bring to bear to understand and predict the ecological contributions to sustainability of our cities, towns, and suburban neighborhoods. Building sustainability into the work of governments in America is still the exception rather than the rule. This is why the Baltimore Watershed Agreement is so important and remarkable. There are a number of political and civic needs for sustainable watershed management and planning (Box 1).
Myth or Reality? Sustainability in urban areas in the ideal sense suggested by ecology is not in fact a reality. In part, this is because urban areas will necessarily draw upon resources and functions beyond their borders. This is true of all settled human ecosystems. There is no way to avoid the need for urban areas to draw on food, fiber, fuel, fresh air and clean water, and the waste processing capacities of ecosystems elsewhere. What is possible for sustainability is for urban areas – including the core city, edge cities, suburbs, towns, and exurbs – to reduce their impact on downstream ecosystems, to reduce the resources used from elsewhere, and to encourage more ecological work to be done within their urban boundaries. Together, such approaches can reduce the net negative effects of settlements, and may even permit cities to produce substantial ecological goods. There is much green space in urban areas that can be protected and whose capacity to slow storm water flows, to absorb nutrients and carbon that would otherwise become pollutants, and moderate the local climate can be put to work. In addition, the psychological calming and recreational benefits of the green components of the metropolis are environmental goods to be promoted The fact that urban sustainability is not yet a reality doesn’t mean that it is a “myth” in the sense of a falsehood or an unattainable ideal. Rather, the idea of myth can be usefully thought of in the way the Ancient Greeks might have. In that classical context, myths did two kinds of work. First, they explained how, or why the world worked as it did. Of course, that use won’t help us today because we have other tools for that. The second purpose of myths does apply now, however. The second concept of myth is as an ethical ideal. Myths indicate how we should behave. They tell what behavior is rewarded, and what kinds of behaviors are to be punished. They delineate good actions from bad. In the sense of an ethical ideal, the concept of sustainability can serve us well. Sustainability of ecological processes, social organization, and economic capacity together can become our shared vision. This vision deserves to be widely taught, both formally in schools, and informally in community and continuing education. It should also better inform the work of the media, since the three components of sustainability (Figure 2) should be at the core of our civic discourse. It will be especially important for us to see sustainability as the yardstick against which the success and rightness of all our actions should be measured. In doing so, we should not neglect the ecological component of sustainability just because social and economic values are more familiar and more widely recognized in urban areas. In fact, the relative neglect of the ecological component of sustainability in the public discourse is all the more reason to emphasize that environmentally motivated strand of resilience and adaptability. Sustainability is a heroic, positive myth of profound ethical and practical importance to the world now. The Watershed Agreement as a Tool for Sustainability The Baltimore Watershed Agreement should be widely recognized, enthusiastically celebrated and embraced, and strategically supported by practical goals. There is great wisdom in this agreement, and with the evident commitment from the Baltimore County and City of Baltimore executives and managers, the chances for success are high. Indeed, there are already strong partnerships with citizen groups and with scientific researchers in the Baltimore Ecosystem Study and other local institutions to be drawn on. I have emphasized the need and power of ecological thinking – the basic concept of sustainability and the powerful ideas of the ecosystem and the watershed – as tools to help assess progress in achieving the goals of the Watershed Agreement. Science will be one of the key anchors for the many partnerships required for this landmark agreement to be realized. As the world enters the first urban century, increasing metropolitan Baltimore’s positive contribution to urban sustainability is a awesome responsibility, and one well poised for success. |
