What will rising sea levels do to the world's megacities?

How major cities will be affected by rising sea levels. Image: Statista/CityMetric.

So you know how sometimes people are like, “this is a good news, bad news kind of a thing”? This isn't one of those times. It's bad news that comes with more bad news behind it. It's a bad news sandwich.

This infographic, made for us by the nice people at Statista using Climate Central data, how sea level rises are going to affect a selection of the world's cities. We've focused on the megacities – that is, those with populations of 10m or more – partly because these are where people are mostly likely to be affected in large numbers, and partly just to manage the size of the map.

The bubbles, and the numbers attached to them, represent the share of the cities' 2010 populations that would be below sea level in the event of particular increases in global temperature. The size of the light red bubble represents the percentage of the urban population that could be submerged in the event of a 2°C increase in global temperature (a degree of increase which feels pretty much inevitable); the dark red one is how much people will be affected by a 4°C increase in global temperature (which we could probably still avoid if we tried, but let's be honest, we probably won't try).

The first bit of bad news is that these figures are very obviously awful. London gets off pretty lightly – but a 4°C increase in global temperature would still put 13 per cent of its population under water. In New York, which is bigger, a full quarter of its population lives in areas that may well be underwater.

But these numbers are as nothing towards some of those Asian cities. In Mumbai and Calcutta it's half; in Shanghai, a city of 23m people, it's more than three-quarters.

In 2010, Dhaka, the capital of Bangladesh, contained an estimated 32m people; in the event of the sort of sea level rise that's expected to follow a 4°C increase in global temperature, 38 per cent of them will be underwater.

In other words, what this map shows is that tens of millions of homes are very possibly going to be underwater at some point before the century is out.

Now you may be thinking, well, could be worse. Okay, Asia's in real trouble here (sorry Asia) but much of the rest of the world is getting off relatively lightly.

Ha. No. Remember, this graphic only shows cities of 10m or more. Some of the world's megacities are relatively safe from sea level rises – Moscow and Kinshasa are both well in-land; Sao Paulo isn't, but it is a long way above sea level.

But a lot of other large cities are excluded because they're not quite big enough to make the cut. A 4°C increase in global temperature would put 26 per cent of San Francisco's population under water. In Tampa, Florida, it's 40 per cent. Barisal, a Bangladeshi city of 7m people, would see 88 per cent of its population submerged by the same increase in temperature.

Perhaps the most terrifying of all, though, are the figures that relate to the Netherlands, a name which literally means “lower countries”. In the event of that 4°C increase in temperatures, 98 per cent of the populations of Amsterdam and the Hague will be below sea level.

Now – below sea level doesn't mean “inevitably underwater”, of course. There are mitigation measures cities can take.

But one of the most important mitigation measures is almost certain to be “moving a lot of people to somewhere else”.

We're in trouble, is basically what we're saying here.


Where did London’s parakeets come from?

Parakeets in the skies above Wormwood Scrubs, west London. Image: Getty.

Visitors to London’s many green spaces would have to be stubbornly looking at their feet to not see one of the UK’s most exotic birds.  Dubbed “posh pigeons” by unimaginative Londoners, these brilliant green parakeets stand out among the fauna of Northern Europe’s mostly grey cities.

‘Parakeets’ is actually an umbrella term referring to the multiple species, which can now be found in London, Amsterdam, Brussels, Paris and various German cities. By far the most common is the Indian ring-necked parakeet, easily recognisable by the stylish red ring around their neck, a matching red beak and, of course, the loud squawking.

In the last 50 years these migrants from South Asia have arrived and thrived, settling into their own ecological niche. In the UK, London is a particular stronghold, but although they may have originally settled in the leafy streets of Twickenham, the birds can now be found in cities as far north as Glasgow.

The story of how they ended up in London is a matter of some discussion and plenty of myth. One often reported theory is that the capitals’ current population are the descendants of birds that escaped from Shepperton Studios during filming of The African Queen, starring Humphrey Bogart and Katharine Hepburn. Others would tell you that they escaped from Syon Park in the early 1970s, when a piece of debris from a passing plane damaged the aviary and allowed them to escape. This chimes with their original concentration in South West London.
My favourite story by far is that they were released by Jimi Hendrix on Carnaby Street in the late 60s. Bored of London’s grey skyline, he set the little fellas free to liven up the place.

However they got here, from 1970 onwards their numbers boomed. In 1992, 700 birds were recorded in London Bird Report. By 1998, 2,845 were seen in the London Area, and by 2006 the ring-neck parakeet was 15th most sighted bird in London.

Darwin would be proud at how well they adapted to the new environment. Toughened up by the hard Himalayan climate, they handle the cold northern European winters better than most locals. Global warming is often brought up in discussions of the parakeets, but it is certainly only part of the story.
It helps, too, that the birds have a 35 year lifespan and few local predators, enabling them to breed freely.

As with any new species, the debate has raged about whether they are harmful to the ecosystem. Strangely reminiscent of the debate over human migrants, often the birds have often been accused of stealing the homes of the natives. The parakeets do nest in tree cavities also used by jackdaws, owls and woodpeckers – but there is little evidence that native species are being muscled out. 

The also provide a food source for Britain's embattled birds of prey. Owls and peregrine falcons have been know to eat them. Charlie and Tom, two city dwelling falcons monitored by Nathalie Mahieu, often bring back parakeets as food.
Of more concern is the new arrivals’ effect on plants and trees. By 2009 their numbers in the UK had grown so much that they were added to the “general licence” of species, which can be killed without individual permission if they are causing damage.

And Parrotnet, am EU funded research project studying the development of parakeet populations across Europe, has warned of the risk they pose to agriculture. In their native India, the parakeets are known to cause widespread damage to crops. As agriculture develops in the UK in line with warmer climates, crops such as maize, grapes and sunflower will become more popular. In India the birds have been documented as reducing maize crops by 81 per cent.

So the parakeets remain divisive. Environmentalist Tony Juniper has disparagingly described them as “the grey squirrel of the skies”. By contrast, the University of York biologist Chris D. Thomas has argued that the parakeets should be left free to move and breed. He sees those wary of the parakeet boom of “irrational persecution” of the bird.

For good or ill the parakeets are here to stay. As so often with migrants of all kinds, there has been some unease about the impact they have had – but the birds, popular amongst Londoners, certainly add colour to the city. Thriving in the urban environment thousands of miles from their natural habitat, they are a metropolitan bird for Europe’s metropolitan cities. 

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