The Value of trees

Tree Facts

Quoted ‘facts’ on the benefits of trees and forests

• UK Government policy on sustainable development includes the measurement of indicators that refer directly to woodland and others to which it contributes. The fact that these indicators are used to measure the quality of life and improvements in the UK economy means the importance cannot be underestimated.
  
  
• Woodland has the ability to contribute to the improvement of 11 of the 15 headline Quality of Life indicators for the UK and 21 of the national indicators. In addition, the area of woodland in the UK, the protection and expansion of ancient and semi-natural woodland and the sustainable management of woodland are national indicators in their own right. Woodland is a major contributor not only to UK sustainable development policy but also to policies on health, education, social inclusion, rural development and biodiversity.
  
  
• The health benefits of walking and cycling in woodland beauty spots are estimated to save the National Health Service up to £4.5 million a year in the West Midlands alone.
  
  
• A study for the South West of England estimated the annual expenditure on day trips and residential courses for woodland education. The South West estimated the financial value of the woodland assets for education to be in the region of £2.26 million annually (1). Based on this, a total annual value of £23.6 million was estimated for the whole of England. This is approximately £372 per 100 school children. A recent study for the Forestry Commission(2)considered the value of the protection provided by forests for archaeological artefacts. The value was estimated to range up to £247 per hectare of woodland. The cultural history, archaeology and heritage in our woodland contributes directly to its value to local communities and to tourism. The interpretation of this aspect of a woodland’s character adds significantly to its enjoyment.
  
  
• Trees have been shown to have a positive impact in the urban environment. The benefits of trees to the community have traditionally been measured through their effect on real estate prices and business profits and it has been estimated that a 20% general tree cover added 7.1% to house prices in rural areas of central England and the Welsh Borders (3).
  
  
• Ancient woodland is home to more threatened species than any other habitat in the UK. The UK Biodiversity Action Plan identifies that broadleaved woodland supports almost twice as many species of conservation concern as any other habitat many species of conservation concern as any other habitat. (4)
  
  
• Visits that are solely for the purpose of visiting woodland are valued at £3.70 per person. It is also estimated that of the 350 million woodland leisure visits each year in England, over a quarter of those will stay long enough to spend money in the local economy.(5)
  
  
• From our research this report recommends the use of a value of carbon sequestered of £59 per tC(6). This valuation of carbon sequestration is widely debated but is taken from the most recent survey of valuation literature in the UK. Another valuation used for carbon sequestration is the marginal benefit per tonne, which varies from £6.67 up to £14.67(7). A third approach would be to use a cost estimate based on the probable environmental damage caused when carbon is emitted. An estimate on this basis is £70 per tonne of carbon(8).
  
  
• More broadleaved woodland on upland slopes can play a positive role in flood control. About a quarter of the rain that falls on outstretched leaves and branches evaporates and the rest drips slowly to the ground and soaks into the spongy leaf mould of the woodland floor, reducing run-off, soil erosion, siltation of lower lying lakes and rivers and the risk of flooding.
  
  
• A study for Northumberland estimated the value of woodlands for flood alleviation at about £1,200 per hectares(9). This estimate is based on the saving which can be made on engineering costs for flood control.
  
  
• Pollutants absorbed by trees includes sulphur dioxide, carbon monoxide, nitrogen dioxide, ozone and particulate matter. Trees and woodland cleanse the air by intercepting and slowing particulate materials causing them to fall out of suspension, and by absorbing pollutant gases through uptake onto inner leaf surfaces.
  
  
• A Forestry Commission study estimated that net pollution absorption by woodland resulted in the saving of 65 to 89 lives per year, and reducing hospital admissions by 45 to 62 per year.
  
  
• The net increase in benefits attributable to pollution absorption by woodland for deaths avoided was estimated to range between £199,367 and £11,373,707 yearly in Britain(10).
  
  
• Water quality is improved by trees through the capture of atmospheric pollution and reduction of the negative impacts of agriculture on water quality. The effect of woodland on water quality helps improve the UK’s river quality, the quality of surroundings and helps to reduce the amount of dangerous substances in wate.

Oxygen & carbon dioxide ‘facts’

• An average metre tall tree will absorb 4.5 to 5kg of carbon dioxide a year. A tree can absorb as much as 21.8kg of carbon dioxide a year and sequester 1 tonne of carbon dioxide by the time it reaches 40 years old. Britain has more ancient oaks remaining than any other country in Western Europe.
  
  Quoted from:- www.forestsofclearedemotions.co.uk
  
  
• One large tree can provide a days supply of oxygen for up to 4 people.
  
  Quoted from:- www.forestsofclearedemotions.co.uk
  
  
• The amount of oxygen produced by an acre of trees per year equals the amount consumed by 18 people annually. One tree produces nearly 260 pounds of oxygen each year.
  
  Quoted from:- www.tree-nation.com
  
  
• In the course of a year one average person produces 704 pounds of carbon dioxide.
  
  Quoted from:- www.faithscience.org
  
  
• An adult man takes into his system from the atmosphere, in one year, no less than 746 pounds weight of oxygen; the calculations of ‘Menzies’ make the quantity amount even more to 837 pounds.
  
  Quoted from:- www.ul.ie
  
  
• Atmospheric concentrations of carbon dioxide have risen to levels which are unprecedented in the recent geological history of the earth. The current level is about 360ppmv compared to a pre-industrial level estimated to be about 280ppmv.
  
  Quoted from:- www.sd-commission.org.uk
  
  
• The current UK forest biomass carbon sink is 2 MtC/yr . This amount of carbon being sequestered by trees in forests is about 1% of fossil fuel emissions.
  
  Quoted from:- www.sd-commission.org.uk
  
  
• In 50 years one tree recycles more than $37,000 (£19,000) worth of water, provides $31,000 (£16,000) worth of erosion control, $62,000 (£31,400) worth of air pollution control, and produces $37,000 (£19,000) worth of oxygen.
  
  Quoted from:- www.tree-nation.com

Facts: Conclusions

• Trees and woodlands are key elements in sustaining the economy, tourism and the nation’s health.
  
  
• Woodlands play a key role in alleviating and restricting flooding as well as atmospheric and soil pollution.
  
  
• Trees and Woodlands meet the UK’s population of 75 millions demands for breathable oxygen. Following the 18 people an acre rule above.
  
  
• The UK’s Trees and woods cannot meet the UK populations required carbon sink. The current UK forest biomass sequesters around 1% of our fossil fuel emissions.

The importance of native trees and their value within the local, regional and national landscape

Water

• The quality of groundwater from Oak woodland at Clipstone Forest in the English Midlands was found to have concentrations of nitrate, phosphate and potassium that were 13 per cent, 5 per cent and 58 per cent respectively of those in water draining a grass field.
  
  
• Riparian woodland( native woodlands along watercourses) provides an effective buffer for protecting streams and groundwater from pesticide applications on adjacent land. It is particularly efficient at intercepting aerial drift of pesticides and trapping pesticides bound to sediment in run-off. Pesticide residues can be removed from drainage water by a number of natural processes within woodland soils, as well as by tree uptake.
  
  
• Floodplain woodland can have a mitigating effect on large flood events, absorbing and delaying release of flood Flows. Mathematical modelling found greater hydraulic roughness created by a 2.2km reach of floodplain woodland on the River Cary in southwest England increased flood storage by 71 per cent and delayed the flood peak progressing downstream by 140 minutes for a one-in-a hundred- year flood event. This was considered significant in potentially protecting downstream sites from inundation.

All quoted from:- www.woodland-trust.org.uk

Air/Pollutants/Soil

• Retention of chemical pollutants on brownfield sites, through use of trees in sustainable urban drainage systems to aid soil infiltration, increase soil organic matter levels, reduce drainage volumes and protect soil from disturbance (taking care to avoid mobilising some pollutants through soil acidification).

Biodiversity

The UK Biodiversity Action Plan states that to maintain the biological diversity of the UK we must

• Maintain the extent of native woodland in the UK (no net loss of one million hectares).
  
  
• Maintain the current extent and distribution of ancient semi-natural woodland, which qualifies as native woodland in the UK (no change in the existing area of 403,000ha).

The importance of native trees : Conclusions

• Creating native woodland in the right place can reduce pollution entering water courses by as much as 90% and has the potential to mitigate large and small floods.
  
  
• Restoring native woodlands alongside other native habitats can reduce
  acidification of water and increase water quantity.
  
  
• Maintaining and managing sustainably the existing area of native woodland will help to preserve high water quality and continue to have a role in reducing floods.
  

Trees and their benefits to local wildlife

• The oak supports at least 280 varieties of insect - more than any other tree. Those living in the bark attract birds, such as great-spotted woodpeckers, to feed. Caterpillars of moths and butterflies eat the leaves. After its death, an oak tree continues to support life. More than 200 varieties of fungi live on the decaying wood, which is also eaten by woodlice and other insects.
  
  Quoted from:- www.icons.org.uk
  
  
• Wood ants play a very important role in the ecosystem of the Caledonian Forest. Where ants have been removed by forest practices, many herbivorous insects can reach numbers out of balance with the rest of the ecosystem and so become damaging to forest trees. . Wood ants have a symbiotic relationship with aphids (for example Symydobius oblongus). The aphids are `milked' by the ants who gently stroke them to get them to release droplets of honeydew, a food that is rich in sugars, acids, salts and vitamins. To the aphids this is their waste product as they have to suck a lot of tree sap to get the protein they require. In return for the honeydew the ants protect their precious sugar source from predators and competing sap sucking insects.
  
  Quoted from:- www.treesforlife.org.uk
  
  
• Pollination is a form of symbiosis that can be observed quite easily. Some insects are fairly specific in their choice of plant. Certain bee species have a longer 'tongue' than others, and this affects their choice of flower. The three banded white-tail bumblebee (Bombus hortorum) (a species found in Glen Affric) for example, chooses deeper flowers such as foxglove (Digitalis purpurea). The shorter-tongued bees can only drink nectar from flowers that are not as deep, such as raspberry (Rubus idaeus) and goat willow (Salix caprea).
  
  Quoted from:- www.treesforlife.org.uk

Seed produced by individual trees & species connections

• An oak will produce its first good seed crop when it is 40-50 years old, and acorn production varies, with trees sometimes producing very few in a given year. Large numbers of acorns are produced intermittently in what are known as mast years, and these occur every three to five years, when a mature tree can produce up to 50,000 acorns.
  
  
• A large Birch tree can produce up to 1 million seeds in a year although only 20% will be fertile. The trees can begin flowering when they are as young as 5 - 10 years old and seed will travel upto 20 miles.
  
  
• Alder produces similar amounts of seed to birch. Foliage provides shade along riverbanks were it often grows. This is beneficial to fish, including salmon (Salmo salar) and brown trout (Salmo trutta), and its leaves, which are relatively quick to decompose in water, provide nutrients for invertebrates such as the larvae of caddisflies, stoneflies and water beetles. These in turn form part of the aquatic food web, and are eaten by larger organisms, including salmonid fish.

Importance of native trees: Conclusions

• Native trees have enormous benefit to the wider environment, far more than non-natives.
  
  
• Oak in particular supports nearly 300 species of insects that responsible for pollination of other plants and crops and as food for birds and small mammals.
  
  
• Oak is also one of the major hosts for over 300 lichens which trap pollutants.
  

Deforestation rates around the world, including uk

• Deforestation – produces 1.6 billion tons of CO2 per year
  
  
• Burning of fossil fuels produces 6.0 billion tons of CO2 www.carbon-info.org
  
  
• From earliest times to the present, the global extent of deforestation has been about 12%. This loss included a 19% loss of closed forest in temperate and boreal latitudes, and a 5% loss of tropical and subtropical forests. The forest cover in wealthier countries of higher latitudes has been relatively stable. In contrast, the rate of deforestation in tropical regions of Latin America, Africa, and Asia have increased alarmingly in recent decades. In 1990, the global area of forest was 4.23 billion acres
  (1.71 billion ha), equivalent to 91% of the forest area existing in 1980. This represents an annual rate of change of about -0.9% per year, which if projected into the future would result in the loss of another one-half of Earth's remaining forest in only 78 years.
  
  
• During this period of time deforestation (indicated as percent loss per year) has been most rapid in tropical regions, especially West Africa (2.1%), Central America and Mexico (1.8%), and Southeast Asia (1.6%). Among nations, the most rapid rates of deforestation are: Côte d'Ivoire (5.2%/year), Nepal (4.0%), Haiti (3.7%), Costa Rica (3.6%), Sri Lanka (3.5%), Malawi (3.5%), El Salvador (3.2%), Jamaica (3.0%), Nicaragua (2.7%), Nigeria (2.7%), and Ecuador (2.3%).
  
  
• These are extremely rapid rates of national deforestation. A rate of forest loss of 2% per year translates into a loss of one-half of the woodland area in only 35 years, while at 3%/year the half-life is 23 years, and at 4%/year it is 18 years.
  Quoted from:- Deforestation - Deforestation Today
  
  
• Woodland is the natural climax vegetation over much of the UK. Indeed, the greater part of the UK was historically covered with woodland until large-scale forest clearances instigated by human activities began around 5000 years ago.
  
  
• Around 15% of UK woodlands (1.5% of total land area) are ancient in origin (i.e. have been continually wooded since at least 1600 AD).
  
  
• Perhaps 90% of the UK's forest cover has been lost over the past 5000 years; forests and woodlands today make up about 10% of the land surface (around 2.7 million hectares). The percentages of forest cover in each UK country are: England 7%; Scotland 15%; Wales 12%; Northern Ireland 6%.
  

UK woodland cover

• Tree cover has been declining for a very long time in the UK - ever since Neolithic man began clearing land for agriculture around 4000 BC. By the Iron Age (500BC) the original total forest cover had probably been halved and had been reduced to just 15% by 1086 when the Domesday Book was produced. Of the remaining ancient woodland a further 45% has been destroyed since the second world war.

Deforestation: conclusions

• Deforestation globally is still happening at an alarming rate. However in the UK, parts of Europe and North America the situation has stabilised.
  
  
• There are many attempts at afforestation around the world, but in the UK we are well placed to not only safeguard new planting through legislation, but to also show by example to other nations that we are trying to put things right for our previous mistakes.