The world’s climate is changing. Storms, heat waves and droughts are also impacting life in central European cities. Further predicted changes are so severe that it is assumed we have entered a new age, the Anthropocene. This term describes the fact that humans, more than any other factors or species, dominate the circ*mstances of all life on the planet.
We are already seeing future global changes occurring in urban areas today. Cities around the world are serving as experimental laboratories. This is because the urban heat island effect anticipates some of the changes that can be expected globally as a result of climate change. Higher temperatures are already being felt in the inner cities, and they are coming up against the effects of globalization, trade, transport, and tourism, with all their knock-on effects, including fragmentation, soil sealing, and densification. This is why cities are seeing the formation of the first hybrid and completely new ecological systems.
Cities are biologically richer than their surrounding areas. This is because plant species are coming into contact with one another in a way that would never have happened without human intervention: on the one hand, there are still remnants of natural and near-natural areas, mostly on the outskirts of urban centers. On the other, many foreign plants and cultivated varieties that have been modified by breeding grow in gardens and parks. Due to the increasing mobility of people, machines and goods, plants also find their way into these modern distribution centers. In cities, we are therefore seeing a melting pot of plants from a wide variety of sources that establish themselves here and form new communities. The result is referred to as a ‘novel ecosystem.’
Plants from warmer and drier areas have inner-city advantages
It is not surprising that neophytes – plants of alien origin – can particularly benefit from these urban climatic effects and from climate change. Plants from warmer and drier areas have advantages in urban areas. That’s why they are part of the image of today’s inner cities. The ability of alien species to disperse spontaneously and establish stable populations can be interpreted as a good indicator of their climate adaptability. But most people want to return to the plant life they are familiar with: they particularly fear neophytes and new plant invasions, i.e. plants that adversely affect native biodiversity. Although this fear is understandable and well-founded, people often overlook that it’s not the neophyte itself that threatens native vegetation, but the conditions that humans have created for these invaders. Invasive plants are particularly successful where the previous species have lost their competitive superiority due to a major change in environmental conditions. In this way, the new plants highlight new potentials that have emerged in a particular place and harness these.
Species that have recently migrated to European cities, such as the princess tree and the golden rain tree, seem completely unfazed by the effect of heat islands, global warming and heat waves in cities. The tree of heaven with its feathery leaves grows even in the smallest concrete cracks and defies heat, drought and air pollution – earning it the nickname “ghetto palm.” And like native plants, neophytes provide ecosystem services, i.e. shade, evapotranspiration and greenery, which we urgently need given the impending changes to the climate. Nature seems, therefore, to have already found an answer to future environmental changes.
Norbert Kühn
