2. Environmental changes and human development
2.1 - Environmental Change
2.1.1 - Human - biosphere interactions
2.1.2 - Biogeochemical cycles
126.96.36.199 - Disturbance in major cycles due to human activities
188.8.131.52 - Carbon
184.108.40.206 - Nitrogen
220.127.116.11 - Phosphorus
18.104.22.168 - Sulphur
2.1.3 - Demographic and economic trends
2.2 - Sustainability
2.2.1 - Measuring sustainability
2.3 - European and Global Dimensions
2.4 - Responses
2.3.1 - The last 20 years
2.3.2 - From problems to institutions
2.3.3 - The way forward
CHAPTER 02 - ENVIRONMENTAL CHANGES AND HUMAN DEVELOPMENT
Environmental change occurs as a result of both natural and human processes. Environmental systems and human activities contribute to environmental changes through the transformation and transportation of large quantities of energy and materials. Natural systems transform the sun's energy into living matter and cause changes by cycling materials through geological, biological, oceanic and atmospheric processes (the biogeochemical cycles described below). Human activities, on the other hand, transform materials and energy into products and services to meet human needs and aspirations.
Compared with natural processes, human transformation of materials and energy has for the most of human history been relatively small. Nowadays, human activities are altering these flows at unprecedented scales; human-induced consumption and transformation of net primary productivity is estimated to be about 40 per cent of that carried out by the Earth's terrestrial ecosystems (Vitousek et al, 1986). Humans fix almost as much nitrogen and sulphur in the environment as does nature (Graedel and Crutzen, 1989). We are also altering the carbon cycle by releasing large quantities to the atmosphere from the burning of fossil fuels. Human emissions of trace metals such as lead exceed natural flows by a factor of 17. The human contribution of other metals such as cadmium, zinc, mercury, nickel, arsenic and vanadium is twice or more than that of natural sources (Nriagu and Pacyna, 1988).
The scale of planetary changes induced by human activities is also evident in the modification of the physical landscape. Since the eighteenth century, the planet has lost 6 million km2 of forests an area larger than Europe (Clark, 1989). In addition, the degradation of land to the point that its biotic function is damaged has increased. According to a recent study from the United Nations Environment Programme (UNEP) the extent of vegetated soil degradation has reached 1964.4 million hectares (17 per cent of the Earth's land area) in the last 45 years, due to overgrazing, deforestation, overexploitation, and improper agricultural and industrial practices (UNEP, 1993). In Europe, the portion of degraded vegetated land reached about 23 per cent of the total over the same period (Oldeman, et al, 1991).
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