What is the NFI and why is it happening now?
Trees, woods and forests are amoung our country's greatest assets. Trees provide a haven for wildlife and people, help mitigate climate change, provide rural employment, and form an integral part of many of Britain’s most beautiful landscapes.
The Forestry Commission is the government department responsible for the protection and expansion of Britain's woods and forests, and our mission is ‘to protect and expand Britain's forests and woodlands and to increase their value to society and the environment’.
To help fulfil this mission, and in accordance with our responsibilities under the Forestry Act (1967), we are undertaking the National Forest Inventory (NFI) of Great Britain. This will help to reveal what the area of existing woodland is, the nature and condition of the woodland and, most importantly, whether the state of Britain’s woodland is improving or declining.
With this information we can better help to protect and increase the value of Britain’s woodland and forests.
What does the NFI entail?
When complete, the NFI will include information gained from aerial photography, satellite imagery, Forestry Commission and woodland owners’ records, and a sample survey of 15,000 1-hectare woodland areas across Britain.
When will the NFI be published
The NFI in its entirety will comprise a range of different products and reports about different aspects of Britain’s woods and forests, and these will be published from time to time as they are completed until 2014. These results will be presented at national, regional and local scales. The first outputs, the woodland area statistics and maps for Great Britain, England, Scotland and Wales have been published.
What use is the inventory?
The information in the NFI is extremely useful to a range of people and organisations involved in land and forest management and planning, policy development and business. Among other things it gives them a "baseline" of information against which they can measure changes. For example, forestry planners working to ensure that our forests are fit to survive likely changes in Britain's climate can use the data to observe changes in woodland species composition over the years which might be caused by changes in the climate.
The forestry and timber industries can use it to update their information about how much timber is growing, where it is growing, what type of timber it is, when it will be ready for harvesting, and similar matters. This enables them to plan ahead for any new investment they might need.
People involved with wildlife and nature conservation can get important information about the state of our woodland heritage, for example, the success or otherwise of programmes to protect and maintain important habitats.
It allows the nation, and individual regions, to see whether their woodland area is expanding, reducing or staying the same. It holds information relevant to the management of pests and diseases that affect woods and forests. And it provides governments with important information on which to base future policies and decisions about woodland management and development, for example, where new incentives might help to encourage certain types of woodland planting or management.
Information gathered for the NFI also helps us to meet certain international commitments that the United Kingdom has made, such as reporting to the United Nations Food & Agriculture Organisation's Forest Resource Assessment process and ForestEurope (the Ministerial Conference on the Protection of Forests in Europe).
How is the information gathered?
There are three main ways in which we gather the information that is fed into the National Forest Inventory.
The first source of information is aerial photography. These can be useful for, among other things, monitoring the expansion or reduction of woodland in the landscape. For example, comparing new aerial photographs with old ones can enable us to spot new areas of woodland that have been naturally regenerating, or where the woodland area has declined.
The second is by a ground survey of a statistically random sample of 15,000 1-hectare (2.5-acre) plots of woodland scattered across England, Scotland and Wales. Surveyors will visit each of these plots once over the five years from 2009 to 2014 to gather a range of information about them. This will include recording the tree and plant species growing in the plots, their numbers, heights, density and the general condition of the woodland. They will return to a random sub-set of plots five years after the first visit to record any changes that have taken place.
The third source of information is a collection of other datasets, such as remote sensing imagery (lower-resolution photos of Great Britain taken by satellite), and owners' own information about the forests.
Has such an inventory ever been compiled before?
Yes, we have been undertaking woodland surveys and compiling forest inventories at roughly 10 to 15-year intervals since 1924. A great deal of change in Britain's woodland and forests has taken place over the decades, so it has been important for us to keep the information up to date with regular new surveys. The inventories used to be known as the National Inventory of Woodlands & Trees (NIWT) and the most recent NIWT report, which was published in 2003, is available at www.forestry.gov.uk/inventory.
Is there any difference between the information gathered for the NFI and the information that was gathered for the previous NIWT?
Yes, there are differences, which explain some of the changes in the statistics. In particular:
- for the NIWT we recorded all woodland areas greater than 2ha, and estimated the national total area of smaller woods in rural regions by scaling up the results of measuring a small sample. We did not include area statistics for small woods in urban areas; and
- for the NFI we have recorded all woodland areas greater than 0.5ha, in urban and rural areas.
For further information please see Previous Surveys.
Why have you recorded and measured small urban woods for the NFI, but you did not do so for the NIWT?
Mostly because we did not have enough financial, staff or technical resources in the 1990s to accurately record all woodland areas smaller than 2ha. There are thousands of them, and many of them are in urban areas. However, technological advances since then made it more practicable and affordable to measure and record them. Also, forestry policy had a greater rural focus in the past, so the greatest need was for data about rural woods and forests. Urban forestry, especially its role in regenerating post-industrial landscapes, has since assumed greater policy importance, with a significant amount of new woodland being established in towns and cities, so there is now a greater need for accurate data about this resource.
So does that mean that the differences between this inventory and the previous one cannot all be attributed to gains and losses of woodland since the last inventory?
Correct. There is a range of reasons for the differences, including woodland gains and losses and those outlined above.
We keep the statistics as up to date as possible between national inventory surveys by tracking changes recorded in Forestry Commission forests and new woodland planting by other owners who receive forestry planting grants. However, sometimes new woodland is planted without grants or other Forestry Commission involvement, although we include an estimate for non-grant-aided woodland planting in our annual estimates. And sometimes woodland naturally regenerates without our involvement, for example, when farmers remove grazing animals from land for some reason, enabling tree seeds to germinate and grow. Similarly, although a Forestry Commission felling licence is required before trees can be felled for a range of purposes, and it is usually a condition of the licence that the site be replanted with trees, a felling licence is not required if the proposed woodland removal is approved by local authority planning permission. These types of woodland gains and losses have not usually been notified to the Forestry Commission, so we usually “catch up” with them when we do periodic photography for the national inventories. However, we are now developing systems for recording local authority-authorised woodland removals as they occur.
Many of the other reasons for the differences can be attributed to improvements in technology and methodology, including:
- the availability for the first time of satellite imagery, which is used especially to quality assure much of the data gathered by aerial photography. Satellites photograph Britain regularly, whereas comprehensive aerial photography is only available every few years;
- the availability of colour photographs of the whole land area of Great Britain. These are now in digital formats that can be manipulated in Geographic Information Systems (GIS). Previous inventories did not have direct access to aerial photographs of all of Britain, and much of what was available was in black and white prints, making data interpretation less easy;
- the availability of photographic imagery at 1:10,000 scale instead of the previous 1:25,000 scale, making wooded areas easier to distinguish from unwooded areas;
- improved GIS software, facilitating more accurate data capture, better quality assurance, and more-detailed reporting; and
- the ability to cross-refer and cross-check NFI data against NIWT data, enabling more accurate analysis and correction of discrepancies. For technical reasons, data from the last NIWT, published in 2003, was not able to be cross-checked against the data gathered for the inventory before it.
What’s the definition of woodland or forest for the NFI’s purposes?
For the NFI we use a definition of forest or woodland as an area of tree-covered land greater than 0.5ha (about 1.25 acres) and at least 20 metres wide whose “canopy cover” or “canopy closure” extends to 20 per cent or more of the land area (or the potential to achieve this). In other words, if the site were viewed from the air, 20 per cent or more of the ground would be obscured by the trees’ foliage when the trees are mature. This definition of woodland is in keeping with other internationally accepted definitions of woodland.
Why are the NFI woodland area figures different to the forestry elements of the CEH land cover map?
A) The NFI is a record of land use, not land cover. So if, for example, a piece of land is customarily used for growing trees, and at the time it was photographed for the NFI its trees had recently been harvested and it was awaiting replanting with new trees, its use is recorded in the NFI as woodland (albeit recorded with a lower, or zero, density of trees). It is important to bear this in mind, for example, when comparing the NFI with some other organisations' records, which might record actual land cover at a particular moment in time, rather than land use. An example of this is the forthcoming Centre for Ecology & Hydrology's (CEH's) land cover figures, which are a record of what is actually on the land on the day it is recorded.
B) Other more specific differences exist between organisations' projects and surveys due to differences in funding, stakeholders, goals and approach. For example the CEH land cover map is a consistent overview of all land use across the whole country at a particular point in time and has therefore opted to use remote sensing images (taken from satellites), whereas the NFI is looking in much more detail at the specific characteristics and composition of woodlands, and consequently uses more detailed aerial photographs as the basis of the survey.
Further details of the CEH and NFI approaches are detailed on the respective organisations' websites.
If a recently harvested area has no trees on it, but is expected to be replanted with trees, is it recorded as woodland or non-woodland?
Please see answer A) under ‘Why are the NFI woodland area figures different to the forestry elements of the CEH land cover map?’.
What happens if the land is never replanted with trees? When do you decide that it is no longer being used for forestry?
We allow 10 years after felling before recording the land as a non-forestry use if it has not been replanted or regenerated by then, unless there has been an obvious and permanent change in land use, such as conversion to a quarry. If the trees have been cleared as part of a project to restore a former land use or habitat, such as wetland or heathland, we allow 10 years for the new land use to become clearly established before we stop recording it as a forestry use.
How is open land within a forest recorded, such as a natural clearing or a rocky mountain top?
For the NFI we record areas of open land that are 0.5ha or smaller and surrounded by forest as a forest use. Similar areas greater than 0.5ha are not recorded as forest.
How does the NFI relate to environmental and other ‘green’ issues such as carbon sequestration, biofuel potential etc?
The NFI is crucial for assessing the current status of Great Britain’s trees, woodlands and forests in relation to all these issues, and for enabling any policies to be formulated in an informed manner. The NFI also provides a benchmark for monitoring the performance of various policies and against various targets in these areas as they progress.
What do the sample survey visits entail?
Each one-hectare NFI survey is typically conducted by one surveyor within one day in a self-contained fashion requiring no input from woodland owners or managers. The surveyor will take a variety of measurements in the wood, such as tree species, tree heights, tree ages and woodland area. We will then use this information to assess the biodiversity value, condition and general health of the woodland, as well as any sustainable timber potential. The timber potential will be fed into the Forestry Commission’s Production Forecast.
How does the sample survey differ from other surveys and/or land access requests (e.g. surveys from other parts of local and central government)?
The NFI has different stakeholders, timescales and reporting requirements from other surveys, so the method and design of this survey are different, as are the locations of survey squares and the funding of the project. As a result, the access requests and survey logistics of the NFI are being handled separately from other projects.
How were the sample survey plots selected?
The plots were selected by a random selection process designed by statisticians and applied to the whole of Great Britain. The number of 15,000 is based on surveying one hectare for every 180 hectares of known woodland. Our statisticians calculate that this is the ratio needed to give us a statistically valid representative picture of the state of Britain's woodland.
If a woodland area that I own or manage is surveyed, will specific details about my woodland be published in the NFI reports?
No, the information collected about your woodland will be treated in strict confidence. The NFI reports are produced as summaries for Great Britain as a whole, for England, Scotland and Wales individually, and for regions in England and Scotland. Therefore any information about your woodland will only be used to contribute to a summary about the woodland in your region, country or Great Britain as a whole - no information about individual woodlands is given.
It is possible that "customised" summary reports for smaller areas than the regions might be produced on request, but these, too, will be written in such a way that no information about any individual woodland or owner will be given.
Can the information about a woodland be used against the owner or manager?
No, the information will not be used to police or regulate any woodland or its owner. The survey is undertaken solely for the purposes of taking a 'snapshot' of the state of Britain's woodland at a moment in time, and does not involve any element of judgement of the merits or quality of anyone's woodland management.
Freedom of Information - Can I get the data for a specific individual survey?
Our policy is to be as open with the information that we hold as possible and we shall be releasing NFI information aggregated to regional and national statistics as and when it becomes available over the next few years via our website at www.forestry.gov.uk/inventory. However, although we do hold information relating to specific individual surveys, this category of information is exempt from disclosure under the Environmental Information Regulations 2004 (EIR) Act, and we are therefore unable to provide it. The reasons for this exemption are:
- EIR 2004 ‘Regulation 12(5) - Adverse effect’, because although we have considered this type of request we consider it is in the greater public interest not to release an individual survey dataset. This is because it will compromise the promise that we have given all landowners on whose land we conduct surveys, namely that information is only ever released in aggregated format. Additionally, without reference to original title deeds it is difficult to know for certain who owns which areas of land to which individual surveys relate. This can be a particular problem in urban areas, where a surveyed woodland area might comprise trees in a number of different ownerships, such as the back gardens of tenement blocks or terraced housing;
- EIR 2004 ‘Regulation 12(9) - The protection of the environment to which the information relates’. This is because we believe that if owners know the results and precise locations of individual survey visits they might manage the survey plots differently between the 5-yearly survey visits from the way they would manage them if they were not being surveyed, and different from any surrounding woodland they also own. For example, they might ‘improve’ the survey plot, but not the surrounding woodland, if they know the precise location and/or results of specific individual surveys. This could create a misleading impression when it is resurveyed five years later that the woodland’s condition has improved, frustrating the aim of the NFI to record a representative sample of woodlands ‘without bias’.
The Freedom of Information Act (FOIA) and the Environmental Information Regulations (EIR) give information rights to any person, anywhere in the world, but the Environmental Information Regulations deal specifically with information relating to the environment. This may include, for example, any decisions, activities and policy formulation that may have an impact on the environment. The definition of environmental information is broad and includes:
- information about the built environment;
- cost benefit analysis of measures and activities which have, or are likely to have, an effect on the environment; and
- any information relating to policies, plans and programmes that affect, or are likely to affect, the environment.
Environmental information is exempt information under section 39 of the FOIA and any request for environmental information must be dealt with under the EIR.
Will the survey cause any damage to land, property or woodland?
No, the surveyors' visits are very low-impact and unobtrusive, and will not damage any trees or plants. The only visible sign that the surveyors were ever there might be a small, discreet peg placed in the ground to provide a reference point for a possible return visit in five years' time to measure any changes. We will consult woodland owners or managers to seek permission to leave pegs.
Do the surveyors need any help from the woodland owners?
We can conduct most survey visits without help from owners or managers. However, where woodlands are some distance from a pubic highway we might ask owners or managers for permission to take a vehicle on to the land to save time and taxpayers' money. So we might need to ask them to unlock gates for us, or provide us with keys so that we can unlock them ourselves. All gates etc will be left the way they were found, and keys returned.
How do woodland owners or managers know when the surveyors are coming?
We will write to them a few weeks before we are due to visit the woodland to make the necessary arrangements.
What if the timing is unsuitable?
If this is the case, the owner or manager should let us know when they receive our letter and we will do our best to reschedule the visit to a mutually convenient time.
Can an owner or manager refuse to give the surveyors access to their woodland?
Although we do have powers under the Forestry Act to enter private land without the owners' consent, we would rather not use them, preferring to make the visits in a spirit of friendly co-operation. If any owner or manager has a particularly strong objection to our surveyors' visiting, we might be able to explore the possibility of visiting another site, but to ensure that the survey is statistically valid we prefer to visit our first-choice woodlands if we possibly can.
What happens if the person who receives the letter no longer owns or manages the woodland in question?
The letter will explain what to do if this is the case. Former owners, managers or agents will be asked, if they can, to tell us the name and contact details of the new owner, manager or agent. Otherwise they should tell us that they do not know who owns or manages it now, and we will try to find the new owner or manager by other means.