The justification for including a short chapter on this topic in a book about wildlife is quite simply that human population increase is much the biggest threat to the welfare of our wildlife in these islands. I also feel that I have some objective comments to make on this topic, having spent a lifetime in academic biology and genetics. The growth of the human population brings with it demands for more food, more water, more power and more urban sprawl, and in the limited space of Britain and Ireland this inevitably leads to a diminishing environmental resource for wildlife. As Sir David Attenborough has so wisely said, “All our environmental problems become easier to solve with fewer people and harder and ultimately impossible to solve with ever more people”.

World and UK populations

The world’s population is currently estimated to be seven billion, having more than doubled since 1960 and more than trebled since 1900. The population in AD 1000 is believed to have been about 275 million, so since then there has been a 25-fold increase. Human population is increasingly concentrated into cities, especially megacities, a megacity being defined as one having a population in excess of 10 million. There is good evidence that migration from rural to urban living is the norm in Britain and Ireland, and that the rate of this movement will steadily rise. There are currently at least 20 world megacities, perhaps a few more, and their combined populations exceed 450 million, so the world is highly urbanised. Indeed, it is reckoned that about half of the present world population live in cities and half in a rural environment. Even if the world population climbs to 9 or 10 billion by the end of this century (it is expected to hit 9 billion by 2050), I think it quite likely that human ingenuity will find ways to feed, house and service this massive population.