Introduction

Having already covered the structure and function of ecosystems, the chapter turns to the environmental problems those ecosystems now face — at the local, national and international level. A broad set of issues is introduced together: over-population, health problems, waste disposal, pollution of every kind, greenhouse gases, ozone depletion, scarcity of water, energy and food, deforestation, climate change, and the pressures of industrialisation and urbanisation. In general terms, an environmental issue is any problem or harmful effect caused by careless human activity and the over-use of the resources nature provides — and the chapter's aim is not just to describe these problems, but to point toward ways of reducing or fixing them. The scale of the challenge is acknowledged internationally: the United Nations regularly convenes summits, conferences and conventions, and roughly 150 countries have signed agreements aimed at cutting back human-caused environmental damage. A recurring driver behind many of these issues is population growth itself — rising demand for food, fibre and fuel has pushed agricultural land use to expand and intensify, which in turn has caused biodiversity loss, land degradation, shrinking fresh-water availability, and, through the greenhouse gases this activity releases, has even begun to alter the planet's own climate.