CUE THE BLOCKHEADS:

Remarkably, this feeding of 7 billion people has happened without taking much new land under the plough and the cow. Instead, in many places farmland has reverted to wilderness. In 2009, Jesse Ausubel of Rockefeller University calculated that thanks to more farmers getting access to better fertilisers, pesticides, and biotechnology, the area of land needed to produce a given quantity of food--averaged for all crops--was 65% less than in 1961. As a result, an area the size of India will be freed up by mid-century. That is an enormous boost for wildlife. National parks and other protected areas have expanded steadily as well.

Nor have these agricultural improvements on the whole brought new problems of pollution in their wake. Quite the reverse. The replacement of pesticides like DDT with much less harmful ones that do not persist in the environment and accumulate up the food chain, in addition to advances in biotechnology, has allowed wildlife to begin to recover. In the part of northern England where I live, otters have returned to the rivers, and hawks, kites, ospreys, and falcons to the skies, largely thanks to the elimination of organochlorine pesticides. Where genetically modified crops are grown--not in the European Union--there has been a 37% reduction in the use of insecticides, as shown by a recent study done at Gottingen University.

One of the extraordinary features of the past 40 years has been the reappearance of wildlife that was once seemingly headed for extinction. Bald eagles have bounced back so spectacularly that they have been taken off the endangered list. Deer and beavers have spread into the suburbs of cities, followed by coyotes, bears, and even wolves. The wolf has now recolonised much of Germany, France, and even parts of the heavily populated Netherlands. Estuaries have been cleaned up so that fish and birds have recolonised rivers like the Thames.

Here's a question I put to school children when I get the chance: Why is the wolf population increasing, the lion decreasing, and the tiger now holding its own? The answer is simple: Wolves live in rich countries, lions in poor countries, and tigers in middle-income countries. It turns out that we conservationists were wrong to fear economic development in the 1980s. Prosperity is the best thing that can happen to a country's wildlife. As people get richer, they can afford to buy electricity rather than cut wood, buy chicken rather than hunt bushmeat, or get a job in a town rather than try to scratch a living from a patch of land. They can also stop worrying that their children will starve and start to care about the environment. In country after country, first in Asia, then in Latin America, and now increasingly in Africa, that process of development leading to environmental gains has swiftly delivered a turning point in the fortunes of wild ecosystems.

One way of measuring such progress is to look at forests. Forests are still being cut down in poor countries, but they are expanding in rich ones. It turns out that when a country reaches a certain level of income, around $5,000 per person per year, it starts reforesting. This is because people become wealthy enough to stop relying on wood fires for cooking and to use electricity or gas instead. Bangladesh, for example, was desperately poor in 1980 but is now rich enough to be significantly increasing its forest cover today.

Overall, therefore, the number of trees in the world is steadily increasing. A study published by NASA and the University of Maryland in 2018 examined satellite data and found that global increases in tree cover have more than offset losses in tree cover over the past 35 years. This is not just because of growing plantations of timber crops; most of it is natural regeneration. Nor is this happening only in the cold woods of the North; tropical countries are reforesting as well. If you had told me in 1980 that this would happen, I would not have believed you.

In 2013, I caught wind of an interesting study being done by NASA in conjunction with Boston and Beijing Universities. A team of researchers had found a way of measuring the quantity of green vegetation on the surface of the planet using satellite data. It was increasing: there were more green leaves each year. I published an article on this phenomenon of "global greening" and was immediately vilified for my impertinence in departing from the pessimistic script. But in fact it had been clear for some years that the carbon dioxide levels measured on top of a mountain in Hawaii, though increasing year over year, were also rising and falling with the seasons more than they once did, implying there was more growth of green leaves in the northern hemisphere summers.

In 2016, the same team published a paper confirming that global greening was occurring and speculating about the cause. Although the press release that accompanied the paper preemptively admonished me--by name!--for taking any comfort from this fact, it quoted the lead author, Zaichin Zhu of Beijing University, saying that the greening over the past 30 years was equivalent to adding a new continent covered in green vegetation twice the size of the United States. Global greening is occurring in all ecosystems, including rainforests, tundras, and croplands, and it is particularly strong in the arid areas of the planet.

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