ABSTRACT

Introduction Satellite pictures of the Earth clearly show that far more of its surface is covered with sea than with earth. The oceans cover just over seven-tenths of its surface, but what the satellite images fail to show is that half is covered by ocean deeper than 3000 m. At present, apart from the transit of shipping and a small amount of oceanic fishing, this half of the world’s surface remains largely unused by humans, albeit modified to some extent by anthropogenic contaminants (as, for example, clinker, see Chapter 13). Contrast this with the startling data on how little land is now left for natural systems. Allowing for the land area which is covered with ice, or is desert, or is used either agriculturally or for managed forestry, less than one hectare of land per capita of the population (less than 30% of the whole land surface) remains for natural ecosystems (Figure 22.1). This is at the world’s present population size of just over 5 billion. The most optimistic – that is to say, the lowest – forecast of world population is for it to double to 10 billion by 2100; more pessimistic forecasts are for this doubling to occur by 2050! Even using the more optimistic forecast, there will be growing pressure to utilise every usable square metre of land, including most National Parks and Nature Reserves, within a few decades.