City and urban ecosystems

Michael is taking an evening walk in his neighbourhood. He wishes it was summer already so that he could go camping with Leon again. He really likes being surrounded by nature, but there isn’t much nature in the city... Cities differ significantly from the natural world. In cities, people design the surroundings: they decide where streets and buildings are going to be, or whether there is space for a park.

But nature still finds a way to exist here. As a result, cities consist of many elements - living and non-living. Living elements, also called biotic factors, include all organisms, such as plants, animals, as well as us - humans. Non-living elements, or abiotic factors, include air, temperature, weather, but also things made by humans, such as buildings, roads, parking lots, and even light, noise, and rubbish. Together, all these elements make up an ecosystem.

It might seem that nature can’t thrive in cities, and that is true to some extent. But some species have adapted - they have changed their behaviour or even evolved over generations to be better suited for living in towns and cities. Let’s look at some examples. Animals such as hedgehogs, rabbits, and rats are naturally active at night - they are nocturnal animals. They are common in cities, where food is easy to find, and there is less chance of being hunted by predators.

Being nocturnal gives them an extra advantage in a city - they can avoid humans and traffic which pose more danger to them daytime. These animals living in cities, as well as leftover food, can sometimes attract red foxes too. Although in nature red foxes are active mostly at dusk or dawn, in a city they change their behaviour and become more nocturnal too. Other animals that have adapted to living in cities are certain types of birds, such as hawks and falcons. In the wild, they nest on steep mountains or cliffs.

But nowadays, they often build nests on skyscrapers too and lay their eggs there! They hunt mice, squirrels, or pigeons which the cities are full of. For some birds, the street lights actually make it easier to find prey at night! Some organisms, however, can’t change their behaviour. But they can often adapt anyway - through evolution.

A type of very common weed resembling dandelion, hawksbeard, has two types of seeds: fluffy seeds that can float away, and heavy seeds that fall onto the ground close to the parent plant. Hawksbeard in the cities has a greater number of heavy seeds compared to hawksbeard growing in the wild. In the city, the fluffy seeds fly away and so usually land on concrete, where they can’t grow. The heavy seeds usually land in soil next to the parent plant and so can grow. The more heavy seeds a plant has, the more successfully it can spread.

Over several generations, hawksbeard in cities has evolved to produce more of the heavy seeds than wild hawksbeard. Cities steal space from natural habitats and change the environment, so plants and animals have to adapt. But not all living things succeed. Those that don’t are forced to move, or die. However, well designed cities can help reduce their impact on the environment, and become spaces, where humans and nature can coexist in harmony.

All we need to do is be aware of and respect the nature around us, even in cities. Then, who knows what you might discover, wherever you live!