Urban deforestation and what we can do about it
Nadina Galle
Author of THE NATURE OF OUR CITIES | 2025 National Geographic Explorer | Ecological Engineer (PhD) | TEDx & Keynote Speaker | Forbes 30 under 30 🌿
dWhilst many think that deforestation happens only in the Amazonian jungle or deep into the heart of Borneo, our cities are facing tree loss at a massive and unprecedented rate.
Urban deforestation as a result of human activity not only decreases the health and quality of life in our cities, but it also worsens the effects of an unpredictable changing climate. Urban trees protect our cities from the effects of harsher storms and more intense heat waves, creating more resilient cities in the process. Not to mention that they actively sequester carbon dioxide and pollution.
In the past, it was quite difficult to measure just how much green urban space we were losing each year. It was also not considered of the utmost importance for many hell-bent on development at any cost. However, with today’s technology, we now know that each year US cities lose over 36 million trees. Globally, that number is likely to be well into the hundreds of millions.
But what’s causing urban deforestation and what can we do about it?
Deforestation can be defined as the process of clearance or clearing trees permanently to make way for something other than forest. In an urban context, this can be due to a number of reasons; housing (re)development, unplanned urbanization, or death due to a range of factors. In the United States alone, approximately 175,000 acres per year or 36 million trees per year are removed from urban areas, according to a study released last year.
The effects of urban deforestation stem well beyond contributing to climate change. Trees in cities reduce pollution, stabilize temperatures, and increase real estate value, so when you remove them, you create an environment that is not only detrimental to our health and happiness but also has long-lasting economic impacts.
And like most things in life, these impacts aren’t shared equally across society. Urban deforestation creates what has been called the “green-grey divide” between affluent neighbourhoods with sufficient tree coverage and less wealthy areas that go without.
It has been said that the number of trees in urban areas can be used to assess the relative prosperity of the neighbourhood. “Evidence also shows that the amount of vegetation, known as ‘greenness’, in densely populated areas, can also be an indicator of the relative wealth of a neighbourhood. The ‘grey-green divide’, the contrast between built-up areas with dominant grey colour and green spaces, is taken as a proxy indicator of sustainable management of cities and planning of urban growth.”
As a result, the corresponding health and lifestyle benefits of living in an area with more trees are passed on to more affluent parts of society. This divide mirrors inequality throughout our society and can actually be seen from space. So, what can we do about it?
When looking at the numbers, many believe that to combat urban deforestation we need to go ahead and plant more trees. However, it’s more nuanced than that. Planting trees is one thing, yet we need to address one fundamental issue at hand: the city is to a tree, what the desert can be to a human; a harsh and volatile place.
Some trees in urban areas struggle to reach adulthood. Yet trees, as iTree puts it, begin to contribute back to society – by sequestering significant amounts of carbon, providing a natural shade canopy and reducing pollution – when they become adults.
So planting trees is not necessarily the answer, or at least, not the nail in the coffin that yesterday’s corporate social responsibility managers tout it to be. So what can our cities actually do about it?
- Hold local authorities accountable for deforestation on their watch. One of the greatest contributing factors to urban deforestation is indifference. It’s so important that our city councils or municipalities take a proactive stance in fighting against the falling of trees across our cities. Yet unfortunately, they are still – even whilst self-identifying as Smart Cities – indifferent to the process of urban deforestation. Creating urban forests takes long-term political will and investment from the side of the local authorities. Local authorities must be held accountable for the deforestation that happens on their watch.
- Ensure the local population is informed of the benefits of urban forests. If it’s our local authority’s responsibility to show initiative, it’s our job as citizens to make sure they follow through. Whether we’re talking about Los Angeles, Lima or Lagos cities are made up of citizens. Campaigns that show citizens the benefits of green urban spaces should a) be designed to show immediate benefits to public health and happiness and b) not lecture people about a benefit that they cannot touch or see; climate change or resilience.
- Take advantage of rapid advances in forestry management technology. With the advent of industry 4.0 technologies like artificial intelligence and the Internet of Things, cities can use technology to both monitor and manage their urban forests. However, according to McKinsey & Company: “state and other public forest owners tend to be relatively conservative in their management style”. By getting out of their comfort zones, cities can take advantage of upcoming forestry techniques and start creating a 21st-century version of best practice.
- Ensure that arborists and tree doctors are equipped to act, not just gather information. So often, the people on the front lines battling urban deforestation are ill-equipped to make a significant impact. Changing this starts with changing the way that cities collect information on their tree inventory. In actual fact, in major urban hubs, a total overview of a tree inventory takes around 3-7 years; half the life of certain street trees. If you only have a handful of arborists at your disposal, it’s imperative that you free up their time from collecting data to acting.
There are so many things happening on the other side of the planet which we have no control over as everyday citizens, public servants and urban activists. What we can do is make sure that we make our own bed before we begin to lecture others about how they should make theirs. This is one thing that we can and must own if we want to build a resilient urban future.
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5yFantastic article Nadinè!
A Passionate Environmental & Nature Photographer, Writer & Naturalist
5yMuch of urban deforestation is happening in the Uk as a result of developers not maintaining their property (inc trees) and poor planning legislation which fails to protect those trees and grounds once planted! A couldn’t careless society !
Nadinè Galle you have skipped right over mentioning the people of which are one of, possibly the greatest, key contributor to the failure of urban trees and who Cities need to make accountable ... Civil Engineers. Civil Engineers, and more notably those that are traditional/conventional philosophy based are taught to design civil infrastructure to mitigate risk. The list is great including, but not limited to: mitigate frequent failure of infrastructure to reduce maintenance costs, mitigate safety hazards, and particularly in respect to this post, mitigate risk to road infrastructure and properties from stormwater ingress and flood risk. For context --------------------- The primary purpose of a road drainage system is to remove the water from the road and its surroundings. The road drainage system consists of two parts: dewatering and drainage. “Dewatering” means the removal of rainwater from the surface of the road. “Drainage” on the other hand covers all the different infrastructural elements to keep the road structure dry. In Sweden “dewatering” is further divided into two parts: runoff (“avrinning”) and dewatering (“avvattning”). “Runoff” covers the water flowing from the surface of the pavement via road shoulders and inner slopes to the ditches. “Dewatering” covers the collection and transport of water from the surface and structure of the road so that there will be no ponds on the road or in the ditches. Source: https://www.roadex.org/e-learning/lessons/drainage-of-low-volume-roads/components-of-road-drainage-system/ ------------------------ And as you will read following, pavements and drainage systems are designed to remove, convey stormwater away from where it lands, as quickly as possible. To keep the sub-soil dry through subgrade drainage, to protect pavements, and other infrastructure against the impacts of soil heaving from differential soil moisture and subsequent swelling. ----------------------- The three most important details to look at when designing a pavement to last: drainage, drainage and drainage. Adequate drainage of the pavement structure is considered to be the most important element in ensuring the long-term pavement performance. The proper design of the drainage system for a particular pavement is of paramount importance. Reducing the moisture content of the granular layer and subgrade through the use of effective drainage directly affects fatigue cracking of the Hot Mix Asphalt (HMA) surfaces and thus the life of the pavement. Drainage of the pavements involves two aspects: surface drainage and subgrade drainage. For urban sections, the paved surface, including shoulders, is crowned and typically drained by a curb and gutter system leading to catch basins which carry the surface flow to a system of storm drains. In addition, the sidewalk or sodded area beside the curb must be graded to drain into the gutter to prevent water ponding in this location. Ponded water on the backside of the curb will seep into and saturate the subgrade at the curbline and may cause increased localized stress to the (pavement). Urban issues In urban sections with curbs and gutters, drainage of the granular layers is prevented as there are no ditches, so subsurface drainage must be used to drain the granular layers. Subsurface drainage must be built in from the bottom up to ensure that it works for the full life of the pavement. The first thing to take care of is shaping the subgrade to promote drainage of the granular materials. If the subgrade is not sloped or it settles after construction (for instance over buried utility services or service connections), water will tend to accumulate in the more porous granular materials at the interface with the subgrade. Over time, this water seeps into the subgrade and may significantly weaken it locally. ----- Then the article talks to sustainable Sponge City Concepts of ‘porous pavement’ but is considered against everything else described in the article. ----- The second application of permeable pavements is called porous pavements. These are designed to reduce or eliminate the surface flow into drainage structures and allows for direct infiltration of precipitation into the subgrade. This concept seems to go against everything described so far. However, this is considered to be a sustainable pavement alternative and has been used mostly for parking surfaces and access roads. Source: http://asphaltmagazine.com/proper-drainage-ensures-lasting-asphalt-pavement-structures/ ---------------------------------------------------------- So, after all this, street trees are provided a little shallow grave aka ‘tree pit’. Surrounded by heavily compacted engineered soils, and drainage all around, almost all stormwater that rains within the traditional urban environment is immediately removed. These trees don’t get enough water to sustain growth. They are fed water (infrequently) via watering carts containing reasonably low-quality water. Poor quality water, infrequent application, results in poor soil and tree health. Picture yourself, a multicellular organism, being fed poor quality water, infrequently. How long do you think you’d last? ----------------------------------- Ongoing City challenges. Things aren’t going to change in this space until Cities’ standards change. City engineers are governed by ‘engineering and development standards’. If a solution for City infrastructure is presented to engineers that differs from these standards, it is more often ‘denied’ approval. WSUD/SuDS standards haven’t changed for nearly two [2] decades. These elements are simply ‘bolted on’ to traditional drainage infrastructure. Frequent rainfall, that prior to urbanisation, was absorbed into the environment, is now sent away from where it lands. Only little volumes are siphoned off to feed the small ‘tree pit plots’ – cautious of not creating a soakage pit. City Mayor’s and Councillor’s are trusted in their engineer’s advice and decisions. Engineer’s are trusted in their standards. Things won’t change until these do. ----------------------------------------- Where to from here Look to Sponge City Concepts as I’ve been involved in for some time. Here I’ve been promoting the requirement of ‘bespoke engineering solutions’ responsive to individual local environments which most practicably 'mimic' natural water cycle processes within the urban environment. I’ve been partnering with Matthew Daniel of Global Urban Forest to ensure that these engineering solutions support long term soil and tree health. But we fundamentally require integration, with all disciplines in the design, approval, construction and maintenance of our urban environments. A silo approach to designing City elements simply isn't sustainable. ----------------------- I recently authored a book chapter on the impacts of urbanisation and conventional drainage infrastructure on the Natural Water Cycle. Whilst related to a case study in Perth, Western Australia, it draws upon general conventional principals and a more sustainable philosophy going forward. https://www.linkedin.com/posts/activity-6642965838385242112-avj8
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5yGood thought. This is why our Accelerating Woodland Creation online conference this Weds has a dedicated session on #woodland in and around urban areas. Join us! http://bit.ly/woodland 20