Award-winning ecologist and author David Goode has an international reputation for his work on urban ecology and was at the heart of biodiversity issues in London for many years as director of the London Ecology Unit and head of environment at the Greater London Authority. A visiting professor at University College London, his most recent book is the widely acclaimed Nature in Towns and Cities (Collins).

As peregrine falcons arrive and sparrows vanish, we need to understand London’s changing biodiversity if we are to protect wildlife. But is the city losing its lead as a centre of urban ecology?

London is renowned for its multitude of green spaces. For a city topping 8.6 million people we are fortunate to have such a remarkable wealth of natural landscapes, ranging from the great expanses of Richmond Park, Hampstead Heath and Epping Forest to the multifarious patches of parkland, commons, reservoirs, woods and wetlands scattered through the capital. Together they make up almost half the area of London. Many only survive today because Londoners fought to protect them in the face of rapid expansion of the city during the 19th century. Those citizens were formidable people, who saw a critical need for public open spaces to be retained in the heat of the industrial revolution. A century later, in the mid 1950s, deliberate planning policies were introduced to protect open spaces as Greenbelt or Metropolitan Open Land, primarily to preserve visual amenity.

Ecology entered the realm of city planning rather late. Action to protect sites of value for nature conservation only took root in the 1980s, though it was obvious long before that London’s open spaces had considerable value for the wildlife they support.

So what happened in the 1980s to change the game? London was not alone: a new philosophy of urban nature conservation was sweeping through towns and cities and the capital became one of the leading players. This new approach was radically different from the essentially science-based practice of nature conservation that had become well established and remarkably successful in rural areas. In the urban environment, the value of nature to people in their local surroundings became a key issue. So, as well as traditionally valuable patches of ancient woodland, meadow and heath, it was recognised that other quite unassuming habitats, such as overgrown cemeteries, abandoned railway land, or even the wilder parts of a town park could provide significant opportunities for people to experience nature close to home. The new movement was firmly rooted in support from local communities and individuals who valued contact with the natural world in the place where they lived. Creation of new habitats was another key element. Spectacular results can be seen at the London Wetland Centre in Barnes, or Camley Street Natural Park, a tiny oasis at the back of St Pancras station that has had an extraordinary influence on the local area.

In 1982, I found no mention of ecology, wildlife or nature in any official planning document in London

When I joined the Greater London Council as its first Senior Ecologist in 1982, I found no mention of ecology, wildlife or nature in any official planning document in London. The next ten years saw a massive shift in public opinion in support of nature conservation, greatly encouraged by campaigns led by the London Wildlife Trust and reflected in the strength of local opposition when treasured sites were threatened. For the first time, the social value of nature was given formal recognition by inspectors at public inquiries, resulting in a succession of landmark decisions that gave boroughs the confidence to challenge detrimental proposals.

By the early 1990s every borough had a chapter on ecology and nature conservation in its local plan. Most boroughs relied on specialist advice from the London Ecology Unit, which provided a unified London-wide approach and gave advice on hundreds of planning applications every year. The Unit will probably be best remembered for its publications containing detailed descriptions of all the important wildlife areas in the capital. They were in effect an ecological equivalent of Pevsner. Together there are over fifteen hundred designated wildlife sites with varying degrees of protection, including 140 Local Nature Reserves. In total they cover almost a fifth of London. In 2002 this model was adopted as the biodiversity strategy that forms a crucial part of the statutory London Plan.

So we know a great deal about habitats, but what about species? I have no doubt that Britain’s long tradition of natural history investigation paved the way for greater awareness and understanding of nature in the urban environment. Richard Fitter’s classic volume on London’s Natural History in 1945 was a brilliant demonstration of the way nature responds to the multitude of activities taking place in a great city. He exposed a whole new world to Londoners, but his analysis would not have been possible without the huge body of knowledge compiled by members of the London Natural History Society over the previous century. That work still continues today and it forms the bedrock of our understanding of trends and changes affecting species.

Some 13,000 species have been recorded in London over the past fifty years and distribution maps have been published for the most popular groups of species, such as birds, plants, butterflies and moths, as well as more obscure groups. Birds are particularly well documented. The total number of species breeding in London fluctuated considerably during the 20th century. It is hard to believe that nightingales, shrikes, nightjars and wrynecks nested on inner London commons until just before the First World War. Shrikes must have been commonplace when Richard Jefferies casually mentioned two pairs on telegraph wires a short distance from Clapham Junction in 1880. But they, and many other species, disappeared as London’s growth took its toll on heathland and woods. Yet during the latter half of the century many new species became established, including a great variety of wetland birds such as little egret, cormorant and little ringed plover, together with introduced waterfowl, notably mandarin duck and several varieties of geese.

Colonisation is one of the key features of urban ecology. In London, the species that instantly spring to mind are foxes, ring-necked parakeets, Canada geese and peregrine falcons, all of which have been studied in great detail. The peregrine’s move into London must rank as one of the most dramatic stories of recent years. They first nested in 1998 and the steady growth in numbers has resulted in nearly twenty breeding pairs today. Their success is due in part to a change of behaviour, after they found that the lights of the city allow them to hunt by night, so enabling them to catch migrating birds that were previously safe from predation. They have become truly urban birds, and in so doing they have entered our lives in a spectacular fashion. These are iconic birds, the fastest birds in the world, whose unrivalled superiority on sea cliff and mountain, and regal status in falconry among princes, kings and emperors, has given them a special place in our imagination. Now we have them sitting in full view on top of Tate Modern and the RSPB provides telescopes at the Millennium Bridge to watch their antics. Live webcams in other cities have made it possible for millions of people to follow the lives of peregrine falcons; they have entered the digital age.

Peregrine falcons, the fastest birds in the world, sit in full view on top of Tate Modern

During the past twenty years, dramatic declines have affected some of our commonest species such as house sparrow, starling, song thrush, swift and hedgehog. These trends have all been highlighted by the work of amateur naturalists in a process now referred to as citizen science. Understanding the causes of such declines is more difficult. Many different explanations have been suggested to account for the widespread catastrophic decline of house sparrows in many cities since the 1980s. One is that an increasing level of particulates from traffic emissions has reduced the amount of invertebrate food available to nestlings. Increased numbers of sparrow hawks may also play a part. Swifts may have declined due to the lack of suitable nest sites in modern buildings, but reduced numbers might result from factors affecting them in Africa, where they spend most of the year. We may not have all the answers regarding the causes, but we are quick to pick up the trends.

So where are we now? London’s ecology is extremely well documented and, on a world stage, the Biodiversity Strategy is second to none. With more than 1000km of footpaths and cycleways forming green chains linking open spaces and nature reserves, Londoners have remarkable opportunities to visit and enjoy a rich variety of wild landscapes. There are even suggestions that London should become the first National Park City, respecting the natural world alongside city living. That is a great idea that deserves serious consideration.

The fact that nearly 50% of London’s land area is undeveloped is not just an attractive feature of the city; it is crucially important to its functional economy. Ecology and economy are closely linked. Most obvious is the value of flood plains. Where they still exist as open land, flood plains are vital in reducing the risk of flooding. Build on them, and it is not only the new developments that will be in danger of flooding but all the adjacent areas that were previously protected by a flood plain.

Another example is the value of green space, especially woodland, in mitigating the extreme effects of global climate change through temperature amelioration. Detailed assessments of the economic value of these ‘ecosystem services’ have produced some startling figures. Atkins environmental consultants have estimated that the ecological services provided by Camley Street Natural Park for free are worth £2.8m per year! There is much talk of building cities that will be resilient to climate change. In my view the fact that London already has a high degree of resilience as a result of its ecological landscapes, known as the green infrastructure, give the city a colossal benefit worth billions of pounds.

What does the future hold? Predictions suggest that London will have a population of eleven million by 2050. New schools, housing, hospitals and business parks all require land. Pressure for new housing is already acute and targets are set to rise. Government policy gives brownfield land high priority for development, yet many areas of this kind have high biodiversity value and are also hugely valued by local people because they are the only accessible open spaces in already heavily built-up areas.

Some boroughs no longer have ecologists to advise them. Planning committees desperately need such specialists

For all these reasons, borough councils need to stand firm in defending the existing biodiversity strategy. They should also aim to double the number of Local Nature Reserves by 2025. Recent cuts in public expenditure mean that some boroughs no longer have ecologists to advise them. The skills and knowledge necessary to make an ecological case have gone. Some councils have even lost sight of the reasons for ecological designations. Planning committees desperately need such specialists.

The economic value of ecological services needs to be voiced with conviction, to convince decision-makers of the need to protect these valuable assets. That will require a major cultural shift in our perception and use of London’s green spaces. I suggest that the concept of a National Park City should be pursued with vigour, for it is only by having a radical vision of this kind that Londoners will appreciate what they have and what could so easily be lost.