How Planting Trees in West Berkshire Can Offset Carbon Emissions by Dr Mike Morecroft, Natural England


There is wide recognition of the threat posed by climate change and the need to act urgently to reduce greenhouse gas emissions.  Reducing emissions is however not enough as some emissions remain very difficult to eliminate completely.  It is therefore important to also take greenhouse gases, particularly carbon dioxide, out of the atmosphere to achieve ‘net zero emissions’.  

The government has now changed the target in the Climate Change Act from 80% emissions reduction by 2050  to achieving net zero emissions by 2050; in other words any remaining emissions must be balanced by actions that take carbon out of the atmosphere.  Forests are an essential element of this – trees naturally take up carbon dioxide from the atmosphere and use it to produce wood.  

We can therefore make a significant contribution to achieving net zero emissions by creating new woodlands and a number of interested residents are investigating the opportunities to do this in West Berkshire.  The initial idea is to create new forest on 1% of the area of West Berkshire.

How much carbon can woodlands take up?

Much information is available about carbon uptake by woodlands. The Woodland Carbon Code, support by the Forestry Commission sets out a well respected approach to estimating it.

Much depends on the choice of species, growing conditions at the site, site management and the time interval being considered.  Young woods take up carbon more quickly than mature woodlands.

1 hectare (ha) of mature natural woodland takes up approximately 6-7 tonnes of carbon dioxide per year – roughly the annual emissions of an average British person (note the standard unit is tonnes of CO2 equivalents, CO2e, to take account of other greenhouse gases).  A young wood will take up more however, so, for example, in the first 30 years an oak wood can take up as much as 17 tCO2e/ha/y in good growing conditions at close spacing and without thinning.

Fast growing conifer plantations can take up more carbon compared to native broad leaved species over typical forestry rotations. Maximising carbon uptake needs to be considered alongside other reasons for creating woodland.  A conifer plantation may be a good way to produce timber and take up carbon but will be less good for biodiversity and recreation, so is unlikely to be suitable for a community woodland project but may be attractive to a land owner seeking a return from selling timber.

In addition to carbon in wood, soil carbon will also increase by approximately 0.5 tCO2e/ha/y when establishing new woodland on arable land.

Diagram of the woodland carbon cycle from The EcoSystem Carbon Cycle of a Forest Plot in Wytham Woods by Fenn, K., Malhi, Y., Morecroft, M., Lloyd, C. and Thomas, M. (2014) 

These questions will need to be looked at in more detail and professional advice taken for a project of this scale.  However, a reasonable starting point might be to aim to take up 12 tCO2e/ha/y over the next 30 years.  

One average person’s emissions at current rates could therefore potentially be captured by approximately 0.5 ha of new forest over the next 30 years.

How much difference will this make?

Given the population of West Berkshire is about 160,000 and the area is 70420 ha, creating new woodlands on 1%  (704 ha) of the land in West Berkshire might capture about 1% of emissions.

This is clearly not enough in itself but emissions from electricity supply are falling dramatically and starting to fall in other areas, including transport. We can also realistically aim for a greater increase in new forest area, over 30 years, perhaps 5% of the land.  The Committee on Climate Change’s scenario for meeting the net zero target include overall UK forest cover increasing from 13% to 17%.

It will be important to decide the role of any specific project.  It is likely that there will be financial incentives for private land owners to increase forest cover anyway.  A community based project has the opportunity to complement this by finding additional land, engaging the community and to be a pioneer, learning and sharing lessons with others.

It is also worth noting that there are many other measures which the local community can do to reduce greenhouse gas emissions, including through energy efficiency, dietary change and encouraging low emissions transport.

What happens in the long run – isn’t the carbon released back to the atmosphere?

Whilst the tree grows the wood stores the carbon.  If the tree is harvested and the timber used for construction or for example furniture making, the carbon continues to be stored.  If it is burnt it is released to the atmosphere but it may replace the use of fossil fuels.  In a natural, unmanaged forest, the wood decays naturally; some of the carbon will become part of the soil and some returned to the atmosphere.  New trees also replace old ones; turning agricultural land into woodland will therefore store carbon for the long term, even though the rate of net uptake declines as the woodland reaches equilibrium (which would take well over 100 years)

What are the options for creating new woodland?

Trees can be sourced from tree nurseries and planted.  Woodlands can also be created through natural regeneration – simply allowing tree species to colonise open ground naturally.  This is potentially cheaper and easier and works best in extending existing woodlands which provide a good source of seeds.  The downsides are that it can take longer and species may not be the ones which we would have chosen.

Planting density of trees varies but could be approximately 2000 per ha.  We would therefore be looking at something like 1.4 million trees to afforest 1% West Berkshire.  This is a lot of trees and we might want to think about creating our own tree nursery locally.

Species choice is important – native or non-native species, but also the seed source – whether local or from further afield.  Climate change adaptation to ensure new woodlands survive and grow well in our changing climate is important.  Similarly it is important to reduce the risks from pests and diseases.   A mixture of species will make for greater resilience.  A range of native trees species, including those known to be resistant to drought and warmer temperatures would be a good starting point, perhaps including both local seed sources and those from further south.

Fencing is likely to be important to protect new woodlands from grazing animals, particularly deer and can be a large cost.  This will need to be factored into plans.

We will want to ensure new woodlands provide a variety of benefits in addition to carbon – wildlife, places for people to visit and enjoy and potentially also providing benefits in reducing flood risk.  We might also want to stimulate new local business opportunities working with timber from the woods.

These factors will all affect where are the best places to create new woodlands.  It is also important to consider what the land is currently being used for: we would want to avoid the most productive agricultural areas and those which are important for biodiversity at the moment.  There will inevitably need to be a degree of opportunism and working with supportive land owners and local communities will be essential.

Opportunities for funding and support

It is already possible to get grants for planting trees under the Countryside Stewardship scheme.  The government is looking to replace this with a new system of funding which will reward land owners and managers who use the land to provide public goods.  This will include carbon uptake and storage, as well as biodiversity and other benefits.

Carbon offsetting is an emerging area that we could hope to benefit from – if we are certified to meet Woodland Carbon Code standards it would be possible to offer the opportunity to offset greenhouse gas emitting activities like flying by contributing to woodland creation.

The government is developing plans for a new Nature Recovery Network, including large Nature Recovery Areas, which could be a good opportunity.

There are a wide range of local and national trusts and other charitable sources that would also be likely to be interested in supporting a project of this sort, for example the Greenham Common Trust.

I would be keen to use a project like this as a research and learning opportunity: the UK will need to transform its approach to land use and management and we can be a pioneer of this if we start now.

Dr Mike Morecroft

Dr. Mike Morecroft has spent most of his scientific career doing research on the impacts of climate change on the natural environment. He currently works for the government conservation agency Natural England, is an Honorary Research Associate at Oxford University, and a lead author for the Intergovernmental Panel on Climate Change. He is also a Hungerford resident and a licensed lay minister at St. Lawrence’s Church.


One Response

  1. Very interesting article. Do your calculations take into account the tree loss from ash die back & other diseases expected in the coming years?
    Also, do you have any advice on alternatives to plastic tree guards?

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