文章来源：Lighten up, Sir David. Our wildlife is safe
FALLING POPULATION, MORE WILDERNESS IN 2100
Published on: Sunday, 15 September, 2013
Sir David Attenborough's pessimism is misplaced
My recent column in the Times addresses the demographic transition and land-sparing:
1 Publicising his imminent new series about the evolution of animals, Sir David Attenborough said in an interview this week that he thought a reduction in human population during this century is impossible and “we’re lucky to be living when we are, because things are going to get worse”. People will look back in another 100 years “at a world that was less crowded, full of natural wonders, and healthier”.
2 His is a common view and one I used to share. He longs for people to enjoy the open spaces and abundant herds of game that he has been fortunate enough to see. To that end he thinks it vital that there should be fewer of us.
3 Ever so politely, I would now passionately disagree with the two premises of his argument. It’s actually quite likely, rather than impossible, that population will be falling by the end of this century and it is also quite likely that the people alive then will have lots more wilderness to explore and wildlife to admire than today.
4 The rate at which world population grows has roughly halved from more than 2 per cent a year in the 1960s to roughly 1 per cent a year now. Even the total number of people added to the annual population has been dropping for nearly 30 years. If those declines continue, they will hit zero in about 2070 — not much more than 50 years from now. In recent decades the birth rate has fallen in every part of the world. Fertility in Bangladesh has fallen from nearly 7 children per woman in the 1960s to just over 2 today; Kenya from 8 to 4.5; Brazil 5.7 to 1.8; Iran 6.8 to 1.9; Ireland 3.9 to 2.
5 It is still conventional wisdom that the only way to get population growth down is to be nasty to people, albeit with noble motives. You must coerce, bribe, shame or educate them into having fewer babies against their preferences. One country — China — did indeed bring down its birth rate with coercive measures in the shape of a one-child policy. Another — India — tried to introduce coerced sterilisation in the 1960s in return for food aid from America, but was defeated by popular protest and democracy, factors unknown in China.
6 Yet everywhere else voluntary birth control proved a more effective weapon than coercion, and the birth rate came down just as fast. This was because nice things happened: economic growth, female emancipation and, above all, the conquest of child mortality. So long as women have some access to the means of birth control, then one of the best predictors of a falling birth rate is a falling child mortality rate. Once children stop dying in infancy, people plan smaller families. Once they think their kids will survive, they start investing in them, rather than in having more kids.
7 You can see this in the statistics. There is no country on Earth with a child mortality rate below 10 per 1,000 births that has a fertility higher than 3 children per woman; whereas all countries except one (Swaziland) that have a child mortality rate above 100 also have a fertility rate above 4.5. Keep kids alive and you bring down population growth.
8 Which is why the recent plummeting of child mortality in Africa is such good news for Sir David and others with his concerns. Thanks to rapid economic growth, better governance and much improved public health, especially against malaria, most African countries are now experiencing child-mortality falls of 5 per cent or more a year, a rate that is far more rapid than it was in the 1990s. These falls will surely soon be followed, as night follows day, by an even faster fall in birth rates.
9 Europe, Asia and Latin America have already gone through this transition and most countries are producing babies at or below replacement rate of 2.2 per woman, at which population stabilises (without immigration). Africa, for so long written off as a special (basket) case, is following suit almost exactly.
10 For this reason alone, I suspect the world population will stop growing and begin to shrink even earlier than 2070 and almost certainly within this century. But even if it does not, there is good reason to reassure Sir David that our great grandchildren will have more wildlife to look at than he has had. An ingenious study by scientists at Rockefeller University in New York has recently calculated that even with population continuing to grow, and even with people eating more food and especially more meat, we have almost certainly already passed “peak farmland”, because of the rate at which fertilisers are improving yields. (Or we would have done if not for biofuels projects.) We will feed nine or ten billion people in 2070 from a considerably smaller acreage than we need to feed seven billion today.
11 Land sparing is already occurring on a grand scale. Forest cover is increasing in many parts of the world, from Scotland to Bangladesh. Wildlife populations are booming in Europe (deer, bears, boar, otters), in the polar regions (walrus, seals, penguins, whales) and North America (turkeys, coyotes, bison, geese) and this is happening fastest in the richest countries. According to one recent report, animal populations grew by 6 per cent in Europe, North America and Northern Asia between 1970 and 2012, while shrinking in tropical regions. There is almost a perfect correlation between the severity of conservation problems and poverty, because the richer people get, the less they try to live off the land and compete with nature — the less they seek bushmeat and charcoal from the forest.
12 Once again, Africa may spring a pleasant surprise. Over the past four decades agricultural yields in Africa hardly budged while they doubled or quadrupled in most of Asia. That is almost entirely down to a dearth of fertiliser and it is beginning to change. If African yields were to rise, the acreage devoted to farmland globally would start to fall even faster, releasing more and more land for “re-wilding”. The great herds and flocks that so delight Sir David would reassemble in more and more places. The happy conclusion is that making people better off and making nature better off are not in opposition; they go hand in hand.