Note:- UPSC usually asks questions on current trends (eg- Clive Wilkinson’s report on Coral, Current Research Programs etc,  and the content of this article is an attempt in this regard. This particular article caters to Environmental Geography, although can be used in GS paper or any other paper as one sees fit.

One hundred years ago at a meeting of the Ecological Society of America, the botanist Frederic Clements floated a profound and controversial idea.

Instead of plants responding individually to the environment, he believed, they formed communities that acted as organic units. Later, in 1939, he took the idea further with fellow ecology pioneer Victor Shelford, making the case that animals as well as vegetation were part of these organic units, which he was now calling biomes.

The world’s great landscapes are biomes, he argued. The tundra, the desert, the steppe, and the coniferous forest. The concept stuck. Over the years, other ecologists built on Clements’s definition, adding environmental factors such as climate and soil characteristics to the definition; but for the most part, his original vision of biomes as collections of interrelated plants and animals endured.

Yet fundamental to ecology as biomes are, the traditional definition refers only to natural habitats, as if people and cities did not exist. This oversight is causing some to question whether the traditional definitions still apply.

Leading the push for reframing biomes in light of human development is Erle Ellis, an environmental scientist at the University of Maryland. “The concept behind the classic view of biomes is that these global patterns are shaped by climate, terrain, and soils—that sort of thing, but mostly climate,” .

“But when you look at the patterns now, they are not shaped just by climate. There’s a huge amount of shaping going on from human activity. The most extensive one is agriculture: crops and pastures and range lands.”

The idea that human influence was being overlooked came to him in the early 1990s, when he went to rural China to study how the move from traditional to industrial farming was altering the environment.

“Places like that—they are places that, since the last glacial, have not had a natural history. Humans have been using those landscapes for thousands of years and managing the ecology of the whole landscape. So it became obvious there was a lot of ecology that was essentially a human ecology, and the big question was how much of Earth’s ecology has been transformed by our activity.

The answer he arrived at was “almost all of it” and that—on land, at least—natural landscapes have largely ceased to exist. In light of this, he drew a new map of the world’s biomes, one that replaced the traditional grasslands, tundra, and forests with eighteen “anthropogenic” biomes that represented the degree to which humans have altered the landscape. At one end were the few remaining wildernesses, places such as Antarctica. At the other end of the scale, the modern metropolis.

But can cities really be biomes? To fit that definition, cities would need to have similar environmental processes and be home to similar communities of plants and animals regardless of where they are. It would mean that the ecologies of Atlanta, Singapore, and Lagos have more in common with each other than the rural areas surrounding them.

That sounds far-fetched, but the evidence that this could be the case is growing. Take the example of Baltimore and Phoenix. On the face of it, these cities sit in very different environments—Baltimore in the humid East, Phoenix in the arid West. But urbanization has altered their climates. Baltimore has become hotter than the surrounding countryside because of the “urban heat island” effect, while the construction of waterways has made Phoenix cooler. The net result is that air temperatures in Baltimore and Phoenix have become more similar.

Temperature is not the only thing that makes the two cities a closer match than their locations would suggest. The residents of Phoenix and Baltimore have similar gardening tastes, so they opt for the kind of lawns that can be seen in almost every American suburb. The result? Phoenix and Baltimore share similar green spaces with similar plant species.

Water systems also bring cities into line with each other. To build Miami, wetlands were drained, whereas the development of Phoenix saw the construction of lakes and canals. Now, when it comes to water, Miami and Phoenix are more like each other than the Everglades or the Arizona desert.