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I’m having an afternoon trying to work out if we can plant our way to carbon neutrality by 2030. It’s a question Place Directors are asking themselves. I’ve been bouncing ideas around with Tom MacMillan from the Royal Agricultural University (RAU). It’s not straightforward. Let us explain.

If you look out of your window you can probably see a patch of grass. If you can’t then imagine a football pitch.

That patch of grass or pitch is already banked in terms of sequestering – locking up – carbon. Most of the carbon associated with your patch of grass is in the soil.  If you ploughed it up or developed it, you’d release some of that carbon into the atmosphere. Equally you could lock up more carbon by changing how you manage your patch of grass, or growing more plants on it such as hedges or trees. But it’s crucial to remember your main carbon asset is already sat underground – investing in better land management and more vegetation is as much about protecting that, as it is about sequestering more. The grass, shrubs or trees above ground are the icing on the cake.

So, for example, you could plant your football pitch with trees. The net sequestration is the difference between grass and trees, minus the carbon you release from the soil when you’re planting them. For the first 10-20 years the trees aren’t adding much over and above the grass as the saplings are growing and putting on wood slowly. In fact, it’s probably 20-30 years before you start to get significant new carbon locked up. You might get net gain quicker if you mixed in native grassland, wetland and / or saltmarsh restoration. It would certainly be better for biodiversity net gain.

Back to the question - can we plant our way to achieving net zero carbon by 2030? Simply the answer is no, there isn’t time. And on any timescale, the net gains that changing land use can offer look small against the scale of our total emissions. Indeed, thinking how little ‘headroom’ we’d gain by planting lots of trees puts the staggering scale of emissions – from energy use, transport and so on – into perspective.

In South Gloucestershire we emitted 1,800 kt of CO₂ in 2017. Our early estimates suggest that, with a fair wind, we might lock up 20-30 kt of CO₂ a year through land use change. That’s less than 2%, and assumes that by working with landowners, we find cost effective ways of sequestering more carbon across 20% of land within the district. If we start now, the savings will only just be kicking in by 2030.

The only way to really achieve the 2030 climate emergency target that most local authorities have adopted is to very rapidly decarbonise transport, business and the domestic sector. Indeed, there’s an argument that land use change shouldn’t count towards net zero at all. That 1,800 kt on our books in South Gloucestershire leaves out non- CO₂ emissions, like methane and nitrous oxide, which may amount to another 20% or so of CO₂-equivalent.  The Tyndall Centre recommends that local authorities use land-based sequestration to compensate for non-CO₂ that can’t fully be eliminated, like some level of ongoing emissions from farming.

Does that mean planting trees and improving land management should be a lower priority? Far from it. Even though those non-CO₂ emissions aren’t reported locally, they still exist, and still need addressing if we want to tackle the climate emergency. As some of them come from agriculture, it shifts the focus from simply trying to max out on sequestration by creating woodlands, to supporting a broader transition in land use. That transition should support a range of strategies that combine sequestration with ways of reducing emissions while keeping land productive, and help wildlife recover.

It also matters for the long term. The bigger wins from land use change build after 2030, to the 2050s and beyond. On that timescale they start to make a substantial contribution, and also help us adapt to temperature increases locked in by historic emissions. This longer term view fits with the Climate Change Act 2050 target and the end-of the century horizon for planning ‘grey’ (engineered) infrastructure. It’s worth reflecting on the fact that the Environment Agency’s draft national Flood & Coastal Erosion Risk Management Strategy considers both a 2 degrees Celsius and 4 degrees Celsius increase in temperature by 2100 when planning for flooding and coastal change. Further, the Environment Agency’s climate change guidance for developers and local authorities to support the preparation of flood risk assessments, are based on a 4 degrees Celsius increase in temperature by 2100.This will no doubt become the norm for all providers of grey infrastructure and is the right mindset to be in if you are considering investment in green infrastructure as well. It’s not a quick fix and needs to be thought about in terms of adaptive pathways.

We are in no doubt that investing at scale in green infrastructure is the right thing to do. The aim has to be to ‘turn the curve’ and make sure that there is no more net loss of green infrastructure. Preventing the release of that bulk of carbon already locked up in the soil is critical, let alone the loss of any other wider value, such as biodiversity. Wherever land is developed on the grounds of important economic and /or social benefits, we must also invest in green infrastructure that can offset the historic carbon locked up in the soil and vegetation, and deliver the greatest net gain possible. And we need to remember there will be a lag between releasing the carbon and sequestering it again. We cannot afford to ‘spend’ emissions now and save them later.

Local authorities are legacy investors in their areas and spending on green infrastructure is a classic long-term investment. It has value for carbon offsetting, biodiversity net gain and agricultural production – those pollinators need to move around – as well as providing flood prevention, urban cooling, public health and wider recreational and amenity services. Local authorities own land, can buy land and work in partnership with local land owners to change land uses. The Royal Agricultural University is looking into the options for us in South Gloucestershire.

Having an outrageous ambition for our green infrastructure is not something we can shy away from. An increasingly urbanised world, even if decarbonised, will still require the eco-system services it provides. The deal between urban and rural needs to be recast and only local authorities are truly in a position to coordinate this effort at the local level.

So, what are you going to do with your patch of grass? How are you going to get more public value out of it in terms of carbon, biodiversity and resilience, and how are you going to monetise that net gain and create new long-term income for your authority?

Help ADEPT to help you lead your climate emergency response

What ADEPT wants to know is whether the analysis is right? What have we missed? Who is leading the way in terms of green infrastructure – who is achieving no net loss and successfully helping their communities and land owners to deliver net gain? Who is making a commercial return on investing in green infrastructure? What else do Local Authorities need to help them make the most of green infrastructure in addressing the climate emergency?

Let us know what you think by emailing us at [email protected]