Introduction

The expanding human population (Figure 7.1) has created a wide variety of environmental problems. Our species is not unique in depleting and contaminating the environment but we are certainly unique in using fire, fossil fuels and nuclear fission to provide the energy to do work. This power generation has had far-reaching consequences for the state of the land, aquatic ecosystems and the atmosphere, with

Figure 7.1 Growth in size of the world's human population since 1750 and predicted growth until 2050 (solid line). The histograms represent decadal population increments. (After United Nations, 1999.)

dramatic repercussions for global climate (see Chapter 2). Moreover, the energy generated has provided people with the power to transform landscapes (and waterscapes) through urbanization, industrial agriculture, forestry, fishing and mining. We have polluted land and water, destroyed large areas of almost all kinds of natural habitat, overexploited living resources, transported organisms around the world with negative consequences for native ecosystems, and driven a multitude of species close to extinction.

An understanding of the scope of the problems facing us, and the means to counter and solve these problems, depends absolutely on a proper grasp of ecological fundamentals. In the first section of this book we have dealt with the ecology of individual organisms, and of populations of organisms of single species (population interactions will be the subject of the second section). Here we switch attention to how this knowledge can be turned to advantage by resource managers. At the end of the second and third sections of the book we will address, in a similar manner, the application of ecological knowledge at the level of population interactions (Chapter 15) and then of communities and ecosystems (Chapter 22).

Individual organisms have a physi- ... niche theory,... ology that fits them to tolerate particular ranges of physicochemical conditions and dictates their need for specific resources (see Chapters 2 and 3). The occurrence and distribution of species therefore depends fundamentally on their physiological ecology and, for animals, their behavioral repertoire too. These facts of ecological life are encapsulated in the concept of the niche (see Chapter 2). We have observed that species do not occur everywhere that conditions and resources are environmental problems resulting from human population growth ...

World Populations Histograms

Figure 7.1 Growth in size of the world's human population since 1750 and predicted growth until 2050 (solid line). The histograms represent decadal population increments. (After United Nations, 1999.)

... require the application of ecological knowledge,...

appropriate for them. However, management strategies often rely on an ability to predict where species might do well, whether we wish to restore degraded habitats, predict the future distribution of invasive species (and through biosecurity measures prevent their arrival), or conserve endangered species in new reserves. Niche theory therefore provides a vital foundation for many management actions. We deal with this in Section 7.2.

The life history of a species (see Chapter 4) is another basic feature that can guide management. For example, whether organisms are annuals or perennials, with or without dormant stages, large or small, or generalists or specialists may influence their likelihood of being a successful part of a habitat restoration project, a problematic invader or a candidate for extinction and therefore worthy of conservation priority. We turn to these ideas in Section 7.3.

A particularly influential feature of the behavior of organisms, whether animals or plants, is their pattern of movement and dispersion (see Chapter 6). Knowledge of animal migratory behavior can be especially important in attempts to restore damaged habitats, predict and prioritize invaders, and design conservation reserves. This is covered in Section 7.4.

Conservation of endangered species requires a thorough understanding of the dynamics of small populations. In Section 7.5 we deal with an approach called population viability analysis (PVA), an assessment of extinction probabilities that depends on knowledge of life tables (see Chapter 4, in particular Section 4.6), population rates of increase (see Section 4.7), intraspecific competition (see Chapter 5), density dependence (see Section 5.2), carrying capacities (see Section 5.3) and, in some cases, metapopulation structure (if the endangered species occurs in a series of linked subpopulations - see Section 6.9). As we shall see in Part 2 of this book (and particularly in the synthesis provided in Chapter 14), the determination of abundance, and thus the likelihood of extinction of a population, depends not only on intrinsic properties of individual species (birth and death rates, etc.) but also on interactions with other species in their community (competitors, predators, parasites, mutualists, etc.). However, PVA usually takes a more simplistic approach and does not deal explicitly with these complications. For this reason, the topic is dealt with in the present chapter.

One of the biggest future challenges to organisms, ecologists and resource managers is global climate change (see Section 2.9). Attempts to mitigate predicted changes to climate have an ecological dimension (e.g. plant more trees to soak up some of the extra carbon dioxide produced by the burning of fossil fuels), although mitigation must also focus on the economic and sociopolitical dimensions of the problem. This is discussed in Chapter 22, because the relevant issues relate to ecosystem functioning. However, in the current chapter we deal with the way we can use knowledge about the ecology of individual organisms to predict and manage the consequences of global climate change such as the spread of disease and weeds (see Section 7.6.1) and the positioning of conservation reserves (see Section 7.6.2).

Given the pressing environmental problems we face, it is not surprising that a large number of ecologists now perform research that is applied (i.e. aimed directly at such problems) and then publish it in specialist scientific journals. But to what extent is this work assimilated and used by resource managers? Questionnaire assessments by two applied journals, Conservation Biology (Flashpohler et al., 2000) and the Journal of Applied Ecology (Ormerod, 2003), revealed that 82 and 99% of responding authors, respectively, made management recommendations in their papers. Of these, it is heartening to note that more than 50% of respondents reported that their work had been taken up by managers. For papers published between 1999 and 2001 in the Journal of Applied Ecology, for example, the use of findings by managers most commonly involved planning aimed at species and habitats of conservation importance, pest species, agroecosystems, river regulation and reserve design (Ormerod, 2003).

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