---
title: "what a city's green space is worth, and what the number is for"
canonical_url: https://ensurance.app/guide/what-a-citys-green-space-is-worth
markdown_url: https://ensurance.app/guide/what-a-citys-green-space-is-worth.md
subtitle: "the urban nature declaration counts acres. a valuation counts what the acres do, and for whom"
category: esv
---

# what a city's green space is worth, and what the number is for

*the urban nature declaration counts acres. a valuation counts what the acres do, and for whom*

What is the value of urban green space? London has the best-known valuation. In 2017 the Mayor of London, the National Trust and the Heritage Lottery Fund (now the National Lottery Heritage Fund) published a natural capital account for the city's public green space, prepared by Vivid Economics. It put the gross asset value at more than £91 billion. That is a present value of benefits over time, not a sale price, and it is not on anyone's balance sheet. The account estimated about £950 million a year in avoided health costs. It also found that every £1 local authorities and their partners spent on green space was matched by at least £27 of valued benefit to Londoners.

That is the headline. This post is about what a figure like that is for, and why a C40 city that signed the Urban Nature Declaration should want one of its own. The short version: the Declaration's targets count acres. A valuation counts what the acres do, and for whom.

The parks, the street trees, the river edges and the wetlands exist whether or not a city values them. A valuation is how their work shows up in a budget that is written in money. It is not the worth of the living thing.

:::johnson
**a cover target counts acres. a valuation counts what the acres do.** Two cities can both reach 35% green cover. A map of canopy against heat shows where it falls. A valuation adds what that canopy does for the people under it, and who depends on it.

[see how a city values the nature it owns →](/guide/how-a-city-values-the-nature-it-already-owns?from=guide)
:::

## what the Urban Nature Declaration asks for

The C40 Urban Nature Declaration, launched in 2021 with 31 founding signatories, gives cities two 2030 targets, and signatories commit to one or both. [Funding your city's nature commitments](/guide/funding-your-citys-nature-commitments?from=guide) covers the funding gap behind them. In brief:

| target | what it measures |
|---|---|
| **Quantity** | 30–40% of city surface area as green or blue infrastructure: trees, parks, urban forests, sustainable drainage, permeable surfaces |
| **Access** | 70% of residents within a 15-minute walk or ride of green or blue public space |

Signatories also commit to publishing their nature goals within two years and reporting progress every year.

Both targets are physical. They count area and distance, which is right: you cannot manage what you have not measured. But neither says what the green space does. A satellite study of 96 C40 cities (Martin et al., reported by Eos) found most already meet the cover goal and fewer than half meet the access goal. It also noted that the standard vegetation index from satellites cannot see whether green space is accessible or used.

Cover is necessary. It is not the same as service.

## what a valuation adds

A valuation takes the same acres and asks three more questions.

**What does each acre do?** Stormwater storage, cooling, air filtration, habitat, recreation. Each service has a published value per acre per year, adjusted for the condition of the ground. A healthy urban forest does more than a stressed one. A wetland that floods every spring stores more water than a lawn.

**Where does the work land?** Five acres of canopy in a low-income ward with high heat illness does different work from five acres on a hilltop estate. London's account found that benefits were not spread equally across boroughs. A city with an equity pledge needs that finding at the level of the ward. One caution: benefits valued through property prices or willingness to pay tend to rank wealthier wards first. Check that a ward-level figure is not simply a map of house prices.

**Who depends on it?** The hospital that sees fewer heat admissions, the utility that defers a stormwater upgrade, the transit agency whose tunnel stays dry. That list is where funding comes from.

## what the London account did right

The account was commissioned by the Mayor of London, the National Trust and the Heritage Fund, and carried out by Vivid Economics, with a method others can follow. Two choices are worth copying.

**It used the language of the finance office.** Asset value, annual benefit, benefit per pound spent. A treasurer can read it without a glossary.

**It pointed at a beneficiary.** The £950 million is avoided health cost, about £580 million physical and £370 million mental. Not all of it is cash the health service would otherwise spend, but the health service is the first name on the list of who benefits. That turns an abstract benefit into a conversation with a budget that already exists.

What a city account does not do on its own is turn the number into money for the park. A figure like London's makes the case for a parks budget. On its own, it gives the health service no way to pay the parks for the costs it avoids. That gap, between a measured benefit and a payment, is where most valuations stop.

## from a city account to a funded asset

A citywide account is a strategy document. It tells you that green space matters, in the city's currency. The next step is narrower: one asset, with one set of beneficiaries.

| level | question | who uses the answer |
|---|---|---|
| City account | What is all our green space worth? | Mayor's office, strategy, the C40 report |
| Asset valuation | What does this park, creek corridor or canopy ward do, what would it cost to secure, and who depends on it? | Parks, the capital plan, the funding ask |
| Funding | Who pays, how much, and how does the money reach the ground and the people who care for it? | The beneficiaries, the city, the stewards |

Many cities have pieces of the first row: canopy assessments, i-Tree studies, green infrastructure plans. We have not surveyed the network. Asset-level valuations are rarer, and a way for the beneficiaries to fund the asset rarer still.

The second row is the [natural asset valuation](/guide/how-a-city-values-the-nature-it-already-owns?from=guide). For each asset it returns the annual flows, the cost to secure the ground, the ratio between them, the [value gap](/guide/the-value-gap?from=guide), and the dependents. To be plain: we have not valued a C40 city. The valuation is offered, and the engine behind it has run on real parcels since about 2022. The third row is where ensurance comes in: an account addressed to the asset, so the people who depend on it can fund it. The city's theme lines already exist, including [urban nature](/urban-nature.syndicate?from=guide) and [urban heat](/urban-heat.syndicate?from=guide).

## for C40 network staff

If you work on a C40 network, one method across a cohort of cities makes the numbers comparable. Cities can then see which assets carry which targets and which beneficiaries show up again and again: water utilities, hospital systems, insurers, ports. A shared method is what turns a set of separate studies into a picture of a network, and then into a list of parties who might fund the work together. [Talk to us about a cohort](/contact?from=guide&topic=city-nature-valuation).

## the objection worth answering

"Putting a price on parks invites someone to trade them away." It is a fair worry, and it can come true. The land under a park may be worth more to a developer than the park's stated benefits, and a number can lose that argument. So treat the figure as a floor for the case against selling, never a ceiling and never a price. The danger is a number used without its context, as if the park were worth only what the table says. [A valuation is not the worth](/guide/a-valuation-is-not-the-worth?from=guide). Use it to defend the park, not to describe it.

## frequently asked questions

### what is the value of urban green space?

The value of urban green space depends on the city, the green space and the method. London's 2017 natural capital account put the gross asset value of the city's public green space at more than £91 billion, a present value over time, with about £950 million a year in avoided health costs. In the United States, FEMA's benefit-cost analysis for hazard mitigation uses about $15,487 per acre per year for urban green open space, of which about $7,010 is aesthetic value. The London figure is an asset value for a whole city and the FEMA figure is a yearly value per acre for US grant applications, so do not compare them directly.

### does meeting the 30–40% cover target mean our green space is doing its job?

Not necessarily. Cover measures area. A valuation measures what the area does and where. A city can meet the cover target and still have its hottest, most flood-prone wards underserved.

### how is this different from an i-Tree study?

i-Tree, from the USDA Forest Service, is the standard toolset for valuing urban trees and canopy: carbon, air, stormwater and more. A natural asset valuation also covers wetlands, streams, floodplains and parks, and adds the cost to secure each asset and the list of who depends on it. If you have an i-Tree study, it is a strong input.

## next steps

If your city already has a canopy study or a green infrastructure plan, you have the starting list. Pick the asset you most need to defend in the next budget, and [build out its row](/guide/how-to-build-a-natural-asset-inventory?from=guide). The natural asset valuation is listed on [our services page](/services?from=guide#finance) with its price range.

## sources

- [Greater London Authority, natural capital account for London](https://www.london.gov.uk/what-we-do/environment/parks-green-spaces-and-biodiversity/green-infrastructure/natural-capital-account-london): the account and its findings
- [GLA, natural capital account supplementary document](https://london.gov.uk/sites/default/files/nca_supplementary_document.pdf): method and authorship
- [Heritage Fund, "New figures reveal £91billion value of London's parks and green spaces"](https://heritagefund.org.uk/news/new-figures-reveal-ps91billion-value-londons-parks-and-green-spaces): asset value, health savings, £27 per £1
- [C40 Urban Nature Declaration, city action template](https://www.c40.org/wp-content/uploads/2021/07/2890_Urban_Nature_Declaration_-_City_Action_Template.original.docx): targets and reporting
- [Eos, "Urban nature is often plentiful but inaccessible"](https://eos.org/research-spotlights/urban-nature-is-often-plentiful-but-inaccessible): satellite study of 96 C40 cities
- [FEMA, *Ecosystem Service Value Updates*](https://www.fema.gov/sites/default/files/documents/fema_ecosystem-service-value-updates_2025.pdf) (2022 values): urban green open space per acre per year

## the series

1. [how a city values the nature it already owns](/guide/how-a-city-values-the-nature-it-already-owns?from=guide)
2. [why a city should run an ecosystem service valuation](/guide/why-a-city-should-run-an-ecosystem-service-valuation?from=guide)
3. [how to build a natural asset inventory with the staff you have](/guide/how-to-build-a-natural-asset-inventory?from=guide)
4. **what a city's green space is worth, and what the number is for** (you are here)
5. [price what the creek already does](/guide/price-what-the-creek-already-does?from=guide)
6. [your city is upstream and downstream at once](/guide/your-city-is-upstream-and-downstream-at-once?from=guide)
7. [hire a natural asset valuation for your city or town](/guide/hire-a-natural-asset-valuation-for-your-city?from=guide)