Biodiversity and climate change in North London

By Dennis Ayling, June 2022

This is about a missed opportunity in North London that has repercussions for Inner London boroughs, too.

Everyone now knows we are facing two interlinked emergencies: a devastating decline in biodiversity and catastrophic climate change.

Both threaten our survival, yet both were predicted over 40 years ago. Both are now crises over which we are imminently losing control.

In 1962, Rachel Carson's Silent Spring was published (1).

In 1979, a US National Academy of Sciences report (the "Charney report") found it highly credible that doubling CO2 will bring about 1.5–4.5 °C of global warming (2).  

This spring, the IPCC released the third part of its Sixth Assessment Report (3), looking at ways to limit & prevent human-caused emissions that contribute to global warming. “It’s now or never, if we want to limit warming to 1.5 °C." – IPCC Working Group III Co-Chair Jim Skea 

Why then, one wonders, is the London Borough of Barnet making its biggest mistake of the century in the face of the climate and ecological crisis?
Barnet is failing, at a pivotal moment in history, while all around the world others are producing imaginative and successful solutions to meet current global environmental challenges. The crying shame is that Barnet, with a little more courage, could be an enlightened civic leader for London, the UK and even internationally.

This is not a time to mince words. Let me set the context for my emphatic assertion, and then you should judge whether or not Barnet is passing up the chance to be a world leader in the face of the ecological and climate crisis.

I grew up in Barnet and I spent most of my adult life teaching in schools in the Borough. I have lived and taught in the southern end of Barnet, and I raised my own children and taught in the very green, northern tip of Barnet. I have had a lifelong love for this beautiful part of London. It is this passion for Barnet that compels me to readdress an issue I first raised over 40 years ago. At that time, I was living in Southbourne Crescent. My lodgings there were sandwiched between the rumbling Great North Road and the roaring North Circular Road. However, the rear gardens at Southbourne Crescent backed onto the Dollis Brook, close to where it gives rise to the Mutton Brook and the River Brent.

Let me start with the Dollis Brook, which already shows what is possible, and then go much wider. At Southbourne Crescent, I quickly found that I could walk north from our back garden alongside the Dollis Brook right out to the Totteridge Valley. It was an enjoyable discovery especially as it supported some significant wildlife. As a biologist and a member of the Herts and Middlesex Trust for Nature Conservation I was excited by the potential of this natural corridor. I saw kingfishers at the southernmost end of the Brook and identified aquatic indicator species in the stream that testified to its health. I began to consider how the Dollis Brook might be managed to enhance its wildlife. At the time, most of its length was a mown grass monoculture. Additionally, selective weed killer was being sprayed to maintain the brookside lawn-like appearance. I wrote to the parks superintendent suggesting that at least some areas should be managed like a hayfield to allow a proliferation of wild plants. This in turn would support a greater insect population, bird species, etc. I also advised ending the weed killer spraying because of runoff into the stream and consequent damage to the aquatic ecology. My suggestion to manage the Dollis Brook as an urban wildlife corridor was not taken seriously by the parks department. I tried writing to the local press. I recall at least one of my letters was published but nothing came of that either. However, after many decades, the Dollis Brook is now managed to support wildlife and provides a vital outdoor urban green footpath. So far so good, but what of the massive error on Banet's part?

Indulge me a little longer and I will show how the Dollis Brook, though important, was one element of a wider more profound ecological proposal. After my discovery of the Dollis Brook I started to look at the ecology of the borough more holistically. The north end of the Borough of Barnet is wonderfully green and rich in flora and fauna. Would it be possible to ecologically improve the southern end of Barnet by restoring some of its former green spaces? I have already mentioned that the Dollis Brook bifurcates near Southbourne Crescent. From there, it continues as the Mutton Brook running east and the River Brent flowing west. Both run parallel to the mighty North Circular Road but in opposite directions. At first sight, neither are at all promising as potential wildlife habitats and green footpaths.

Nevertheless, let us take a brief look at the east-flowing Mutton Brook. It immediately ducks south under the North Circular Road running towards Henley's Corner. In the 1970s, this area, too, was mown flat right up to the extremely busy roadside. I suggested planting a strip of woodland on the southern flank of the road to enhance it ecologically and to mitigate the impact of traffic noise and pollution on the green footpath to Henley's Corner. At this point, the Mutton Brook passes beneath Finchley Road. From there, it is a relatively short hop to the extensive Hampstead Heath via Little Wood and Big Wood. A wonderful wildlife corridor and green pathway from the Totteridge countryside to South End Green and Gospel Oak.

Now we can begin to focus on Barnet Council's massive missed opportunity to address the climate and ecological crisis that is now rapidly bearing down on us. Sadly, Barnet has discarded a wonderful chance to green the southern end of its borough and to meet the UN's call to make both local and global transformative change (4). Not only could Barnet have addressed enhancing the ecological diversity of the whole of its urban borough, but it could have made a significant contribution to mitigating the local impact of climate change.

For a moment, consider the current state of the short length of the River Brent that flows within Barnet's boundary.
hand-drawn map of the River Brent near Brent Cross shopping centre
As already mentioned, the Dollis Brook gives rise to the River Brent behind the rear gardens of Southbourne Crescent. The River Brent starts off reasonably well, flowing west through Brent Park, a narrow green wooded strip parallel to the North Circular Road's northern edge. It then passes under Brent Street (A502) to continue between the gardens of houses bordering the North Circular Road and Shirehall Park. This green stretch has wildlife potential, too. However, the next section where the river flows under Brent Cross Flyover and along the southside of Brent Cross shopping Centre to the Brent Reservoir (Welsh Harp) is an utter disaster and has been since I first raised the matter in the late 1970s.

I have already mentioned my early campaign to promote a Dollis Brook wildlife corridor and my efforts to champion it by approaching Barnet Borough's Parks Department and writing to the local press. However, linking Barnet's rural north to Hampstead Heath by enhancing the Dollis Brook and Mutton Brook was only half of my proposal for increasing the biodiversity of Barnet. The other half of my Borough-wide scheme was to have a west wildlife corridor from the Dollis Brook to connect with Brent Reservoir via the River Brent. Clearly, the west branch requires greater effort to refashion it as a wildlife corridor, but it is not impossible. What is more, it would hugely enhance the traffic-blighted southern end of the Borough.

I know for a fact that the full plan to have a north to south Barnet wildlife corridor with both east and west branches at its southern end was put to Barnet Council. Here is how Barnet Council was advised that it could green the length of its borough, especially the southern end dominated by major roads. In the late 1970s, I applied for the post of Head of Science at the former St Mary's Upper School, Hendon. During the interview for the post I was quizzed by Barnet's Science Inspector/Advisor about my interests outside of teaching. I mentioned my membership of the Herts and Middlesex Trust for Nature Conservation and explained my enthusiasm for regreening Barnet, especially its southern end. I was mindful of the social disparity between the deprived southern and the much more affluent northern end of Barnet. The Borough's Science Inspector was greatly taken with my vision of a north/south and east/west linked set of wildlife corridors. He asked me to elaborate in some detail on my full regreening proposal for the Borough. He subsequently put my comprehensive plan to Barnet Council.

After quite some time, when funding became available, the Dollis Valley Greenwalk part was developed. Sadly the other half of my proposal, involving the River Brent, was not taken up by Barnet.

Here is why, in 2022, after COP26 (Climate Change Conference) and with COP15 (Biological Diversity Conference) in China due (5), not carrying out the second part of my plan is a potential disaster. Supporting biological diversity in Barnet by means of borough-wide green corridors is now an urgent local matter as it is nationwide one. The aim being to sustain our rapidly declining wildlife and to give pleasure and healthy recreation to people. These corridors will also be vital in helping to mitigate some of the now inevitable effects of climate change. The section of the North Circular Road adjacent to Brent Cross Shopping Centre is a flood risk area that has seen cars submerged in the past. With the expansion of the Shopping Centre and its increased hard surfaces flash flooding and rain bombs from climate change will bring disastrous inundations. Reflect for a moment on the climate-related flooding increasingly occurring in urban areas around the world. Sydney, Australia is a recent example as is Valencia, Spain. Other more enlightened cities are already taking climate mitigating precautions and becoming sponge cities.

"What if a flood could be something we embrace rather than fear? This is the central idea of Prof Yu's sponge city. Conventional flood water management often involves building pipes or drains to carry away water as swiftly as possible, or reinforcing river banks with concrete to ensure they do not overflow. But a sponge city does the opposite, seeking instead to soak up rainfall and slow down surface run-off." (6)

Hull, in this country, has already adopted this sponge approach (7).

Given the Brent Cross area is dominated by concrete flyovers, hard road surfaces and numerous buildings, it will be prone to retaining heat as well as susceptible to flooding. Introducing an extensive area of vegetation at Brent Cross will not only serve as a flood alleviation sponge but it will also have a cooling effect. Thus, plants are also essential in urban settings to help mitigate the effect of climate related heatwaves.

"Healthy urban trees are known to have a cooling benefit. They do this through the release of water vapour, in the process of evapotranspiration. Trees also provide cooling through the provision of shade and because they reflect more solar radiation and store less energy than many artificial surfaces such as concrete and asphalt." (8)

As already pointed out, the River Brent has three sections to consider in any greening and rewilding programme:
the same map with the suggested nature reserve added
1. The Brent Park section simply needs sympathetic management to maximise its ecological value.

2. The section running through the back gardens of the houses of Shirehall Park needs some expert input. An imaginative scheme to win the backing of residents to garden in support of wildlife should be initiated (9). An incentive such as a reduction in rates might be offered, too.

3. The stretch running under Brent Cross flyover and along the south side of Brent Cross Shopping Centre needs major and radical ecological improvement. It will then not only serve as a wildlife corridor but will double as a sponge flood alleviation measure in the face of climate-related severe rainfall.

Assuming the River Brent continues to flow in a concrete conduit along this third stretch, tree and shrub planting is needed on both sides of it. This will include beneath the flyover. 

Additionally, thought needs to be given to reimagining the present concrete river gully. A totally bald concrete ditch makes for a sterile aquatic environment. There are proven ways to dramatically enhance the biodiversity and amenity value of urban rivers. This is being done all over the world and in London, too. For example, the recent restoration of the River Wandle in Croydon (10). Indeed, a stretch of the River Wandle in Carshalton has won a prize (11). Ecological enhancement measures are described in the links provided in the References at the bottom of the page.

I mentioned reimagining. 
Let us take a moment to visualise what enhancements are possible in a sterile concrete gully. They include recesses in conduit walls for plants and birds to occupy as well as gravel on the conduit floor to provide a substrate for plants.

"Simply removing hard riverbanks to increase riparian vegetation and habitat complexity can improve urban rivers and offer socio-economic enhancements as well. Even where flow rates are not reduced, riparian plants can cool rivers, stabilise banks and offer shade to fish and animals. Hard surfaces in urban areas can limit the amount of riparian planting, but even small amounts on highly degraded sites can significantly improve biodiversity. Introducing gravel substrate in highly constrained locations can provide important linkages for wildlife moving between open space and more natural areas." – European Centre for River Restoration (12)
view of a stream with a brick wall with holes in, and gravel in the stream bed

In some rivers and canals, floating islands have been used to increase biodiversity. Click here and scroll to see instant ecological transformations:

All the large, unused car parks south of this stretch of the river should be dug up, planted and turned into an extensive nature reserve. Not only is this ecologically desirable but it provides the climate change mitigation sponge and heat shield that will be vital here in the future. Additionally, such a greening of the redundant current car parking area will improve Brent Cross Town aesthetically. Furthermore, the roadside vegetation of this new nature reserve will serve as a vehicle microparticle and noise filter from the relentless heavy traffic on the North Circular Road.

It takes some imagination and vision to see a Brent Town Nature Reserve sited between the Shopping Centre and the North Circular Road. Yet pause and reflect on how our roadside verges have taken on a vital role in conserving our flora and fauna.

"Often overlooked and undervalued, road verges can be havens for wildlife, both plants and animals. These narrow lanes of land cover a large area of the UK and are crucial habitats for many rare and declining native species.They have matured into valuable wildlife habitats and corridors." (13)

Bear in mind, too, that all our major road arteries will see a massive drop in gaseous emissions and perhaps noise as we transition to electric vehicles.

Picture for a moment the area in front of the Shopping Centre as a green semi-wooded area. The more isolated areas around the various flyover elements could be managed as wildflower meadows. Visualise a sculptured flight of brent geese along the face of the flyover. Imagine some of the flyover pillars decorated with sophisticated botanical murals. Spectacular transformation is possible to give pleasure, to support mental health and to inspire other urban planners.

The images below illustrate how wildlife motifs can both enhance flyovers and draw attention to wildlife indigenous to their location. These photographs were taken at a flyover on interstate highway (I-35E) at Lewisville, Texas indicating species in Lewisville Lake.
large pictures of fish painted on the side of a raised section of motorway
the same pictures of fish, a closer view
Something like brent geese in flight could be adopted for the Brent Cross flyover (being as they are rare winter visitors to the Brent Reservoir)

two geese flying, black heads and necks
Brent Geese

A true green, tree-lined, walk from Brent Reservoir passing between the south side of the Shopping Centre and the roadside nature reserve would be an immense enhancement. It would then continue along Shirehall Park and through Brent Park to meet with the Dollis Valley Greenwalk.

Finally, a borough-wide scheme to engage residents in garden practices that support wildlife could be also initiated (14). Imagine a permanent Barnet biodiversity/climate exhibition at the Shopping Centre. It would aim to win over residents to become participants in greening the whole of Barnet. Additionally, the exhibition would promote the Borough's enlightened approach to creating green cityscapes that address both ecological and climate issues.

Involving the local community in environmental projects has already proven to work elsewhere. Take Woodbridge, Suffolk for example:

"This project is two-fold. On the one hand we want to create a patchwork of spaces in people’s gardens that are dedicated to, and focus on encouraging, nurturing and protecting biodiversity, that together form the “Community Nature Reserve”.
On the other hand we are trying to find out where we already have wildlife corridors, which will help us to study and improve biodiversity in our beautiful part of the world." (15)

The London Borough of Barnet has a rare opportunity, with the juxtaposition of the River Brent and the Brent Cross flyover section of the North Circular Road, to demonstrate how the most unlikely ugly urban site can be dramatically changed. Brent Cross would be wonderfully enhanced by a 'sponge' nature reserve. Such a transformation would be an exemplary ecological and climate change triumph to inspire cities everywhere.

Finally, there is a wider prospect to my proposal. Already, plans for London's hidden rivers to be resurfaced are afoot (16). Indeed, this has already happened in some places, e.g. the River Wandle in Wandle Park, Croydon (17). The River Fleet running from Hampstead Heath south to the River Thames has been mentioned, as has the River Brent where it passes through Wembley. This holds the exciting future prospect of outer boroughs, such as Barnet, feeding Central London with wildlife diversity through its river corridors.

Mindful of both global warming and a worldwide decline in biodiversity, I put forward my proposals for borough-wide wildlife corridors very early in my science teaching career. I have spent a lifetime involved with children. Now, half a century later, I am still passionately campaigning for our young people's future survival on a restored planet Earth.

With all good wishes for a more beautiful urban world

Dennis Ayling

Dedicated to my grandchild, Damon Atticus Allison

The following article concerning the Brent Reservoir (Welsh Harp) has just come to my attention. This area of wetland is a Site of Special Scientific Interest. The article is indicative of the extreme and shameful neglect of the whole Brent River system, especially in the face of the global biodiversity crisis.


(1)  Rachel Carson's Silent Spring published in 1962

(2) In 1979 a US National Academy of Sciences report

(3) This spring the IPCC released the third part of its Sixth Assessment Report 

(4) UN's call to make both local and global transformative change

(5) COP15 delayed until August

(6) Sponge cities embrace floods

(7) Hull's aqua greens are another example of the urban sponge approach

(8) How trees cool towns

(9) Wildlife Gardening

(10) Restoring the River Wandle

(11) River Wandle wins prize

(14) Creating wildlife pathways

(15) Woodbridge's community environmental projects

(16) Restoring London's Rivers, 2008

(17) Restoring London's Rivers, 2016