By Dr. Alison Blyth and David Evans
In an inner city street a fox melts into the night in search of a meal. Maybe it will catch a rat, an animal equally at home among the trash cans and concrete alleys. Across the world, some animals who once lived among fields and forests are following the human trend for city living.
For other animals, our fondness for towns and roads, industry and parking lots spells decline and death.
What do these changes mean for conservation and how can we make the best of our changing environment?
An Urbanized World
Urbanization – the process of converting undeveloped land into cities and towns – has been described as “one of the most ecologically destructive forms of global change”. However, urban areas are also the world’s fastest growing category of environment. While wilderness and even farmlands are declining, cities and towns are spreading as human populations grow.
Urbanization affects every facet of a natural environment. Land cover, drainage, and nutrient cycles are all fundamentally altered, and even parameters such as temperature can be changed as buildings replace vegetation.
Natural habitats for many species are destroyed, degraded, or broken up into pockets. The remaining areas of vegetation are often fragmented, disconnected, and lacking in the mature complexity of a long developed natural area – all factors that reduce biodiversity and wildlife resilience.
Unfortunately, the areas where we centre settlements are also areas rich in wildlife – we, just like other animals, seek good environmental resources. We seek out running water, good soils, liveable climates, access to coasts and transport routes. These optimal environments are often also those with the highest biodiversity. Our most destructive form of change is preferentially affecting some of our most environmentally precious lands.
If you can’t beat them, join them
Despite urbanization’s potential for negative effects, some ecologists see the fight against the concept as a lost cause.
“As a species, we want to urbanize”
explains Bill Bateman, a behavioral ecologist specializing in urban wildlife at Curtin University, Australia.
“Humans have been congregating in settlements and later in towns and cities since the earliest stages of our history. The majority of people want to live close to resources and facilities.”
Bateman argues that, since we can’t avoid urbanization, the priority is to make the process work hand in hand with preserving biodiversity and wildlife.
“This is one of the most important challenges facing conservation today.”
Embracing the new
The first key in building conservation minded cities is understanding exactly what effects these changes have on different wildlife populations.
“People assume urbanization is negative across the board, but there is actually huge variation in response depending on the animal in question”
Bateman explains. One crucial factor is that although cities represent highly changed environments, they also represent new environments – and sometimes these “novel ecosystems” provide exactly what an animal needs.
Bateman’s favorite example of this is urban predators. Work undertaken with Trish Fleming of Murdoch University showed that urban environments can provide hunters with new advantages – for example, new and increased numbers of prey species as animals such as rats and mice exploit their own urban niche; and improvements to hunting patterns allowed by anthropogenic structures.
It isn’t just predators who can gain surprise benefits from human changes to their environment. Recent work by Euan Ritchie and his team at Deakin University showed that southern brown bandicoots, an endangered Australian marsupial, are defying expectations to thrive on the outskirts of Melbourne. An extensive monitoring project showed that the small mammals were more successful in new and altered sites consisting of parks, gardens and road verges than they were in sites reflecting their natural environment.
A key facet in a species’ ability to thrive in new and changed environments is their adaptability, and especially their flexibility of diet. Bandicoots for example, mostly eat insects, but aren’t that fussy. Like their northern analogue, the hedgehog, they’ll happily scarf down dog and cat food if they come across it. Likewise, the red fox, one of the ultimate urban predators, will happily top up from trash bins if a fresh meal isn’t handy.
Greening the city
Although urbanization will always have negative effects on some animals – known as urban avoiders for their inability to live in human altered habitats – development doesn’t always have to be bad news. Provided, of course, that it is planned with one eye on conservation.
A major aspect in improving urban environments is increasing green space. These spaces may be planned parks but can also be easily forgotten areas such as road verges and railway corridors. Ritchie’s bandicoots were frequently found nesting in the blackberry bushes alongside roads. The simple presence of thick vegetation, even in this case an invasive weed, enhanced the conservation value of this human dead space.
Increasing green spaces is beneficial to humans living in urban areas too.
The WHO notes that access to urban green spaces such as parks has a positive effect on physical and mental health, while there are also pragmatic, economic benefits. Increasing tree cover in a city mitigates the heat island effect where reflection of sunlight from buildings and hard surfaces increases urban temperatures. And shade from street trees can reduce energy bills from air conditioning.
Urban vegetation also improves drainage and water run-off, reducing flooding risks. And of course, retaining local and regional biodiversity is not an abstract benefit. Humanity is dependent on ecosystem services such as pollination, and we unbalance that ecosystem at our peril.
Unfortunately, this message has not got through to all urban managers. Parks are closing because they take up precious building land or because councils can no longer afford maintenance.
Building trends lean more and more towards block filling fence-to-fence building design, maximising internal space but squeezing out green gardens in favour of a limited entertainment space. In cities across the US, trees are under attack due to maintenance demands, or complaints about the inconvenience.
The frustrating thing about this for scientists such as Bateman is how simple many steps to improve urban conservation could be.
“Road verges and railways corridors are an obvious easy win. We literally don’t have to do anything, just let nature take its course. We’d even save money on maintaining them!”
Encouraging gardens, planning for communal green spaces, encouraging green building design and permeable land coverings are also all obvious options.
As Bateman says,
“Achieving more wildlife friendly urban spaces is easier than we think if we embed awareness of conservation and biodiversity as a normal part of life. We just have to want to do it.”Dr Alison Blyth is a geochemist working in earth and environmental sciences.
David Evans is an environmentalist and the co-founder of Tern Goods – A reusable alternatives company specializing in recycled and repurposed shopping bags invented to replace single use plastics.
Image Credit 1) ecosystemsunited.com