Why more cities need to add up the economic value of trees
Your parents were wrong: money does grow on trees.
Cities routinely rake up tens of millions of dollars from their urban forests annually in ways that are not always obvious. Leafy canopies lower summer air conditioning bills, but more shade also means less blade to maintain thousands of acres of grass. Health-wise, trees contribute to lower asthma rates and birth defects by removing air pollutants.
Across the nation this Arbor Day, city foresters should celebrate trees as economic drivers and get past the false dichotomy of economy versus environment.
Portland, New York City, Milwaukee and Atlanta are among the cities that have quantified the payoff from pines and palms, olives and oaks. It’s part of a breakthrough in thinking among city planners in recent decades who now realize that a city runs not just on engineering, but on biology and ecology as well.
What’s a tree worth?
Tampa, Florida demonstrated that kind of thinking in moving its leading tree official, Kathy Beck, from the Parks and Recreation Department onto its chief planning team. Tampa approaches trees as part of a green public works system, the living equivalent of roads and bridges. It’s a case of what Beck calls “green meets gray.”
Part of how Tampa gets it right on trees is that planners can shield themselves from partisanship, protest and profit motives by relying on science to decide on what, where and how many trees to plant.
To get the biggest bang for tree planting and maintenance bucks, Tampa turns to my colleague, University of Florida Institute of Food and Agricultural Sciences urban forester Rob Northrop, for information on which trees provide the greatest shade, which can be planted closest to sidewalks and parking lots without root growth buckling pavement and which species best withstand floods in a city already impacted by sea level rise. University of Florida scientists Michael Andreu, Andrew Koeser and Paul Monaghan and the USDA Forest Service’s Geoff Donovan have also provided valuable expertise.
Northrop and other natural resource scientists see intrinsic value in trees. But he recognizes the tremendous economic pressures communities are under, so he and economists collaborate to get at the straight-dollar costs and benefits.
The most recent study of Tampa’s trees estimated that they save the city nearly US$35 million a year in reduced costs for public health, stormwater management, energy savings, prevention of soil erosion and other services.
Drilling down even further, the University of South Florida has begun mapping individual trees. So planners know, for example, that the live oak on the 4200 block of Willow Drive has a 38-inch diameter and a $453 annual payoff.
Coping with urban growth
Through the painstaking work of compiling an inventory of a city’s green infrastructure, policymakers can make more informed decisions on where to focus resources.
Just as the most decrepit or most used roads get more attention, key trees might get pruned or watered more often. Tampa has assessed the health of trees that line its evacuation routes. This kind of information would have been valuable to transportation officials in the San Francisco area, for example, before a commuter train was recently derailed when it struck a fallen tree.
Other cities recognize the importance of urban forestry. The Atlanta Tree Conservation Commission, for example, is appointed by the mayor and City Council to oversee urban forestry. Portland, Oregon, has a Parks and Recreation Urban Forestry Division that manages and regulates 236,000 street trees and 1.2 million park trees.
But in general, few cities employ people with deep expertise in urban forestry.
The Society of American Foresters didn’t start accrediting university programs in the discipline until 2005. There’s not even consensus on a definition of urban forestry, though Beck, from Tampa, describes it as the science of addressing both people with tree problems and trees with people problems.
In coming years, the nation will continue to grow and urbanize. One study suggests that in the next half-century, seven million acres in Florida alone could convert from rural and natural to urban use.
The push into formerly natural areas will bring with it more impacts on trees. At the same time, we’ll need trees more than ever to create and maintain livable cities.
Let’s love our trees. More than hugs, they need science. The quiet efforts of planners and scientists are our best bet for green cities that inspire us to marvel year-round at the natural canopies above us and the ground beneath our feet. Happy Arbor Day.
Oslo’s ambitious ‘climate budget’ sets the bar for other cities
Oslo’s city government has issued an ambitious “climate budget” with the intent of halving its carbon emissions from 1990 levels by 2020, and becoming completely carbon neutral by 2030. To achieve this goal, the city plans to limit access for cars with new tolls and fewer parking spaces, power the bus fleet with renewable energy, increase cycle use and eliminate heating with fossil fuels in homes and offices.
The move comes at a time when cities are taking on a more important role in addressing the issue of climate change. Globally, cities are thought to be responsible for roughly 75% of human-sourced carbon dioxide (CO₂) emissions, because urban populations still depend largely on fossil fuels to generate energy. Since CO₂ is the chief greenhouse gas, cities are considered to be key drivers of global climate change.
Yet cities are also uniquely well-placed to address this issue; most cities have their own planning systems, which can be used to manage the local economy and the urban landscape (that is, land-cover and land-use), in order to regulate energy use.
Until relatively recently, policies to measure and reduce greenhouse gas emissions were administered at a national level, to ensure compliance with international agreements, such as the Paris Agreement. But over the last decade, cities have started to play a bigger role in global efforts to tackle climate change.
A new protocol
This is evident in initiatives such as the Global Compact of Mayors, of which Oslo is a member. The compact – founded by UN Secretary General Ban Ki-moon and former New York City Mayor Michael Bloomberg in 2014 – is a coalition of cities and local governments that are voluntarily taking action to combat climate change and move toward a more resilient, low-carbon society.
To come up with effective policies for reducing emissions, cities first need a way to inventory their energy use. To that end, the compact has created a protocol that classifies energy use into six main sectors: stationary (for example, building construction and use); transportation; waste; industrial processes and product use; agriculture, forestry, and other land use and any other emissions occurring outside the boundary as a result of city activities.
These categories account for the greenhouse gas emissions associated with burning coal, gas, oil and so on. But they also take stock of the gases that are taken out of the atmosphere by plantations and forests, for example.
Completing a greenhouse gas inventory using the protocol can guide urban policies to reflect the character of a city. For example, cities in cold climates use more gas and electricity to heat buildings in winter, while low-density cities generally dedicate more energy to transportation, and cities with a strong industrial base expend energy on manufacturing.
Becoming carbon neutral means reducing or even eliminating fossil fuel use, reducing landfill waste and offsetting any remaining emissions. Typically, the strategies involve incorporating aspects of technology (such as renewable energy generation), design (for instance, making cities more compact) and behaviour (for example, shifting commuters from private to public modes of transport).
In the case of Oslo, its population of about 650,000 people emits roughly 1.34m tonnes of CO₂ per year, with much of this energy expended to meet building and transportation needs. While the plan to reduce emissions to zero is very ambitious, it’s worth keeping in mind that Norway already generates the majority of its electricity using hydropower.
This gives Oslo options that other cities may not have. For example, adding to the electric car fleet is a common policy in many cities concerned about air quality and greenhouse emissions. But if the electricity is produced by fossil fuels, then electric cars simply shift the creation of greenhouse gases from moving transport to stationary charging points.
Likewise, most of Oslo’s homes are heated with electricity generated from hydropower, and by burning wood pellets, which are also considered to be a renewable fuel. Here, the challenge is to make homes more efficient, and to ensure that more fuel for direct and indirect heating comes from renewable sources.
There is much to be learned from Oslo’s progress; in particular, it highlights the need for tailored policies and plans, to address the unique emission profile of each city. Yet the city will still need to overcome significant barriers, to become carbon neutral by 2030. In particular, it will need to offset any residual emissions through forestation, or by actively capturing carbon at the source.
Yet Oslo’s carbon budget raises the stakes for other cities which are working to combat climate change. The greenhouse gas protocol provides a consistent, transparent and internationally recognised approach for cities to measure and report emissions, allowing for credible comparison – and a little healthy competition – between urban areas across the globe.