Search Results

This chapter looks at the assessment of biological change due to man's activities. It asks: what is normal situation and what are the limits of expected variability? Has there been a change from the normal situation and, if so, can that change be quantified and statistically tested? Is the degree of change significant and can it be related to one particular stress, or general environmental perturbations? An estuarine ecosystem health assessment (or monitoring) programme requires an analysis of the main processes of the ecosystem and the identification of known or potential stresses. In order to be scientifically valid, it requires the development of hypotheses about how those stresses may affect the ecosystem, followed by the identification of measures of environmental quality and ecosystem health, needed to test the hypotheses.

This chapter summarizes what is known about the abiotic environment of the Serengeti ecosystem as it changes over different scales. This chapter first looks at the broad scale, then looks at physical change, and considers how changes at these different scales affect the ecology of the Serengeti ecosystem. Geological events shape the physical landscape and the parent material forms the chemical properties of the soil. Climate events shape the system and act on many scales. For example, droughts historically dried up Lake Victoria and altered weather patterns. However, changes have also been human, such as the change in Mara River’s water flow due to increased agricultural use upstream. All in all, this chapter gives two recommendations based on these events and changes: to allow wildebeest and other migrants access to the lake shore, and to carefully plan and manage the human land use of the Serengeti ecosystem.

Themes that characterise urban wetlands in this century are: an association with human activities, especially development, education, and culture; invasive species management; migratory species feeding and breeding grounds; recognition by international environmental agreements; restored or constructed wetlands; and a role in providing for a focus of sustainability in the urban system. The chapter sets those themes in the context of the emerging paradigm of ecohydrology and the application of the ecosystem approach of the convention on biological diversity. For wetlands, especially in an urban context, understanding the linkage between ecology and hydrology — ecohydrology — is an important new way of thinking. Four key points that define ecohydrology are: understanding that ecosystem change is inevitable, and the role of people in managing change; integrating water and biodiversity science at management relevant spatial and temporal scales; understanding the role of ecosystem services; and defining and understanding the links between green and blue water. The role of blue and green water in an urban setting is also linked with human generated grey and black water, and linkages between these waters result in a range of semi-natural and artificial (or constructed) wetland ecosystems in urban landscapes. Human health in urban areas also depends on having well-functioning and well-managed ecosystems to provide a range of ecosystem services that support both human health, but also the health (functioning) of other ecosystems and their components. The chapter also identifies ten urgently needed research directions.

This chapter examines whether Tamarix is a passenger (that is, it achieves its dominance by tolerating or capitalizing on changes in the ecosystem that are outside the sphere of influence of the plant itself) or a driver (the species can dominate an area by its own alteration of the environment to the benefit of itself and possibly other species) of ecosystem change. In particular, it considers the interaction of Tamarix with four ecological factors and how the models of passenger or driver fit with each: regional climate and local weather climate, hydrologic variables, fire dynamics, and the salinity of the soil and groundwater. It suggests that Tamarix in the US Southwest is both a passenger of and a driver of ecosystem change based on its impact on hydrology, climate change, fire, and salinity. Whether this view of a combined passenger-driver model for Tamarix invasion holds for the leading edge of the species's expansion remains unclear.

Unsustainable situations may result in health outcomes that are mediated indirectly by social, economic, and shared behavioral responses. Social systems exist to mitigate risk: that is why human beings live in communities. The example of the North Atlantic cod fishery is used to demonstrate how an ecological catastrophe (in this case, the depletion of fish stocks) resulted in serious health effects through a process mediated indirectly by social mechanisms. This was an economic “bust” of historic proportions, but economic “booms” also bring sustainability issues. A “boom town” is a community that experiences a sudden influx of people, direct investment, and expansion of the local economy that places severe demands on the local infrastructure. A useful analytical framework of this type of problem is called “DPSEEA.” This chapter develops a more elaborate version called “DPSEEA+C” as a device for problem analysis in sustainability.