Forestry in numbers

Forest and woodland cover 12% of the UK. Of this total, 47% is in Scotland, 40% in England, 10% in Wales and 3% in Northern Ireland. Between 1996 and 2007 the area covered by forest and woodland increased by 4%.

Vulnerabilities - Overview

The increased vulnerability of forests (and people) with respect to climate change refers to several impacts (28,34):

• Forest cover: conversion of forests to non-woody energy plantations; accelerated deforestation and forest degradation; increased use of wood for domestic energy.
• Biodiversity: alteration of plant and animal distributions; loss of biodiversity; habitat invasions by non-native species; alteration of pollination systems; changes in plant dispersal and regeneration.
• Productivity: changes in forest growth and ecosystem biomass; changes in species/site relations; changes in ecosystem nitrogen dynamics.
• Health: increased mortality due to climate stresses; decreased health and vitality of forest ecosystems due to the cumulative impacts of multiple stressors; deteriorating health of forest-dependent peoples.
• Soils and water: changes in the seasonality and intensity of precipitation, altering the flow regimes of streams; changes in the salinity of coastal forest ecosystems; increased probability of severe droughts; increased terrain instability and soil erosion due to increased precipitation and melting of permafrost; more/earlier snow melt resulting in changes in the timing of peak flow and volume in streams. The capacity of the forest ecosystem to purify water is an important service, obviating the cost of expensive filtration plants.
• Carbon cycles: alteration of forest sinks and increased CO2 emissions from forested ecosystems due to changes in forest growth and productivity.
• Tangible benefits of forests for people: changes in tree cover; changes in socio-economic resilience; changes in availability of specific forest products (timber, non-timber wood products and fuel wood, wild foods, medicines, and other non-wood forest products).
• Intangible services provided by forests: changes in the incidence of conflicts between humans and wildlife; changes in the livelihoods of forest-dependent peoples (also a tangible benefit); changes in socio-economic resilience; changes in the cultural, religious and spiritual values associated with particular forests.

Productivity

Increasing CO2 concentration can affect tree growth through increased photosynthetic rates and through improved water-use efficiency. There will be complex interactions, however: forest growth rates may well be increased in some cases by rising levels of atmospheric CO2, but rising temperatures, higher evaporation rates and lower rainfall may lower growth rates in other cases (19).

Non-timber products

Increasingly there are concerns about the productivity of non-timber products such as medicines and foods. Relatively little information is available in the scientific literature about the sustainable management of such products, and even less is known about their vulnerability to climate change (28).

Windstorm damage

Under the assumption that the wind climate will not change, the risk of windstorms for forestry between now and 2100 will increase considerably in the UK, due to higher exposure and higher vulnerability (36).

Vulnerabilities - Forestry

Hotter, drier summers, milder wetter winters, rising CO2 levels in the atmosphere, and more frequent extreme weather events such as flooding and storms could result in changing forest productivity. These impacts are likely to be positive in the north and west and negative in the south and east. This may lead to changes in the identity, location and productivity of commercial forests affecting the timber processing industry. There will be increased frequency of water-logging in winter limiting access for management activity and enhancing the risk of wind blow and changing frequency and severity of tree disease and insect pest outbreaks. Changes will also be seen in the distribution of species and the composition of native woodland vegetation communities (1).

Application of the selected UKCIP98 climate change scenarios led, for the 2050 low emissions scenario, to a complete loss of xeric woodlands/scrub, a reduction in temperate conifer and boreal evergreen forests, but an expansion of temperate deciduous forests and temperate/boreal mixed forests. For the 2050 high emissions scenario, the area of temperate conifer forest is restricted to the highlands of Scotland and the remainder of the country is covered by temperate deciduous forest with temperate/boreal mixed forest predominating around coastal regions. This is explained by deciduous trees competing more successfully against conifer trees as winters become milder and the growing season becomes longer and warmer (2).

The East of England has 7.3% woodland cover, compared to the highest cover of 14.1% in the South East, and the lowest cover (outside of London) of 5.1% in the East Midlands. Temperature and rainfall, which determine water availability, are likely to have the greatest impact on woodland. Certain species will fare poorly whilst others will do well. For example, in terms of productive woodland, yields of Corsican Pine are predicted to increase, whilst Scots Pine is likely to decrease (3).

Pests and diseases may become more prevalent, although complex interactions between trees, pests/pathogens and their predators or natural controls make predictions hard. Scope for commercial forestry could be limited by water availability, as woodlands typically have higher water demands than other land uses. However, trees could play a role in adapting to climate change and mitigating potential impacts. For example, through providing shelter belt functions and as a means of stabilising river banks and reducing erosion in riparian habitats (3).

For Scotland changes in rainfall and the consequent soil moisture regime may be significant in south east Scotland but is of less interest elsewhere because of the high existing rainfall, though waterlogged ground may become more common particularly in autumn and winter (4). Excess wind has a major negative impact on forests while higher atmospheric carbon dioxide concentrations are likely to improve growth rates. The key uncertainty in the likely response of forestry to climate change is the variability and rate of change in climate.The most serious risk to forestry from climate change appears to be the possibility of more extensive wind-storms leading to more blow-down and limitation of tree height.

West and Gawith (5) present an overview of expected climate change impacts on several activities for different regions of the United Kingdom, based on several regional scoping studies. The results for forestry are listed below. A blank cell indicates that no specific issues were identified for the region besidesthose noted in the first row.Each region identified and discussed issues differently, so this table might not provide comprehensive coverage of all issues.

Region Expected positive impact on forestry Expected negative impact on forestry Uncertain impact on forestry Majority of regions Increased growth and productivity Increased risk of storm damage. Increased drought risk   South West   Greater risk of fungal diseases   South East   Trees suffer from drier conditions, particularly in chalk downs. More susceptible to pests an diseases   London       East of England   Limited due to water demand Change in species East Midlands   Any expansion will increase demand for water resources   West Midlands Greater opportunities for forestry     Wales   Increased pest problems   North West       Yorkshire & Humber Higher yields may increase employment and possibly profits Shallow broadleafed trees suffer from drought stress   North East   Some tree varieties less suitable. Increased risk of forest fires Different pest species Scotland Shorter rotation times. New species Pests and diseases   Northern Ireland Enhanced biodiversity and balance of trade in timber, especially from agri-forestry    

Vulnerabilities - Peatlands

The British Isles hosts around 10 % of global blanket peatlands. Blanket peatlands often occur on sloping terrain, which makes them highly susceptible to erosion if surface vegetation becomes damaged (38). There are around 3500 km2 of eroded blanket peat in the British Isles (39). Peat erosion impacts water quality leading to high turbidity and heavy metal pollution, disturbed river ecology, sedimentation of reservoirs, and loss of carbon (40). There is therefore a large amount of investment aimed at reducing erosion losses from blanket peatlands (41).

Blanket peat erosion not only results from human action, climate also affects the stability of the peat and associated erosion. The water balance and temperature regime drives the balance between peatland growth and decay. How climate change may affect blanket peat erosion across Great Britain remains unclear, however. A study has shown that the response of blanket peat erosion to climate change during this century will be highly variable in space. Both the relative peat erosion change and absolute erosion risk were predicted to be generally greater in southern and eastern areas than in western and northern parts of Great Britain (37). 

Vulnerabilities – Temperate forests in Europe

Present situation

In parts of Europe with temperate forests, annual mean temperatures are below 17°C but above 6°C, and annual precipitation is at least 500 mm and there is a markedly cool winter period (8). Temperate forests are dominated by broad-leaf species with smaller amounts of evergreen broad-leaf and needle-leaf species (9). Common species include the oaks, eucalypts, acacias, beeches, pines, and birches.

Many of the major factors that influence these forests are due to human activities, including land-use and landscape fragmentation, pollution, soil nutrients and chemistry, fire suppression, alteration to herbivore populations, species loss, alien invasive species, and now climate change (10).

Forest productivity has been increasing in western Europe (11). This is thought to be from increasing CO2 in the atmosphere (12), anthropogenic nitrogen deposition (13), warming temperatures (14), and associated longer growing seasons (15).

Trends

Most models predict continuing trends of modestly increasing forest productivity in Western Europe over this century (16). Projections for the time near the end of the next century generally suggest decreasing growth and a reduction in primary productivity enhancement as temperatures warm, CO2 saturation is reached for photosynthetic enhancement, and reduced summer precipitation all interact to decrease temperate zone primary productivity (17). The projected increased occurrence of pests, particularly in drought-stressed regions, also contributes to decreased long-term primary productivity in some regions of temperate forests  (18).

Sensitivity to increasing air pollution loads, particularly nitrogen deposition and tropospheric ozone, will impact large areas of the northern temperate forest over the next century. In the temperate domain, air pollution is expected to interact with climate change; while the fertilization effects from nitrogen deposition are still highly uncertain, pollutants such as ozone are known to diminish primary productivity (19).

Migration

The ranges of northern temperate forests are predicted to extend into the boreal forest range in the north and upward on mountains (20). The distribution of temperate broadleaved tree species is typically limited by low winter temperatures (21). Since the latter are projected to rise more rapidly than summer temperatures in Europe and North America, temperate broad-leaved tree species may profit and invade currently boreal areas more rapidly than other temperate species.

Carbon sinks/sources

Temperate forest regions in the highly productive forests of western Europe (22) are known to be robust carbon sinks, although increased temperature may reduce this effect through loss of carbon from soils (23). Weaker carbon sinks or even carbon losses are seen for temperate forests in areas prone to periodic drought, such as southern Europe (24).

Models suggest that the greatest climate change threat to temperate forest ecosystems is reduced summer precipitation, leading to increased frequency and severity of drought (25). This will probably be most prominent in temperate forest regions that have already been characterized as prone to drought stress, such as southern Europe. Drought-stricken forests are also more susceptible to opportunistic pests and fire (26). Together, these related effects can potentially change large areas of temperate forest ecosystems from carbon sinks to sources.

Benefits

Globally, based on both satellite and ground-based data, climatic changes seemed to have a generally positive impact on forest productivity since the middle of the 20th century, when water was not limiting (35). Climate change is likely to be beneficial to all types of forestry. The commercial sector will benefit from increased growth rate, resulting in shortened rotation times (4,6).

Young forests are growing faster than older ones on the same sites and in the same climates. About half of that increase in growth may be attributed to the increase in atmospheric CO2 and N deposition that have occurred in the previous century, with a small additional effect of increased temperatures. If this is true, then these forests may be expected to increase in growth further during the next century, maybe by 20-30% by 2050. This prediction of increased growth of conifer plantations in northern Britain may be expected to increase the supply of home-grown timber. At present, about 15% of the timber used in the UK is supplied from UK forests. Any increase in storm frequency or severity would disrupt timber supplies and possibly negate the benefit derived from other changes in climate (7).

By contrast, drier conditions in the south of Britain are likely to have an adverse impact on the growth and maybe the survival of broadleaved woodlands, such as beech and oak. These woodlands showed signs of decline following summer droughts in 1976, 1984 and 1995. Therefore there may be decreased production of high quality hardwoods and greater reliance on imports of this type of timber (7).

Timber production in Europe

Climate change will probably increase timber production and reduce prices for wood products in Europe. For 2000–2050 a change of timber production in Europe is expected of -4 to +5%. For 2050–2100 an increase is expected of +2 to +13% (27).

Adaptation strategies

The Forestry Commission has incorporated climate change as one of the 5 aims for delivering the revised strategy for England's Trees, Woods and Forests (1), with the following objectives relating to adaptation:

• to increase the resilience of trees, woods and forests to climate change;
• to increase the role of trees and woodland in adapting the rural landscape to climate change;
• to enhance the role of street trees and urban woodland in minimising the impacts of climate change on our towns and cities;
• to use trees, woods and forests to help communicate and improve understanding of climate change issues and bring about behavioural change.

Additional adaptation options are mentioned in the scientific literature:

• to avoid sites for forestry that are likely to be affected by increased wind and storm risks or reduced soil moisture/drought (2);
• to use new species and an appropriate species mix (2);
• floodplain forestry may be a suitable adaptation response for continually flooded agricultural land. However, conifers could cause acidification of water bodies which would have negative water quality impacts (6);
• a possible barrier to adaptation response is in defining what constitutes a ‘native’ broadleaved species in a warmer climate scenario (6);
• established forests are reasonably robust, and resilient to climate change. The establishment of new plantations of trees could be affected by soil moisture deficits (6).

In Scotland, the Scottish Forestry Strategy (1) identifies climate change as one of its seven key themes. It sets out three key actions:

• improve understanding of climate change impacts on woodland ecosystems and silviculture, and implement precautionary measures, such as forest habitat network creation;
• maintain preventative measures and ensure readiness for pests, diseases and other threats, such as fire and wind;
• increase the role of forestry in environmental protection including sustainable flood and catchment management, and soil protection.

Early in 2009 Forestry Commission Scotland published a Climate change action plan (2009 –2011) (1). The focus for adaptation is to:

• plan and manage forests and woodlands in a way that minimises future risks from climate change, for example through the creation of forest habitat networks, and using different timber species, including hardwoods, or silvicultural systems;
• assist in environmental protection such as helping to tackle slope instability, reducing riverbank erosion, contributing to natural flood management and increasing the contribution of trees and woodland to climate control in urban areas.

Adaptation strategies - Forest management measures in general

Near-nature forest management and a move away from monocultures toward mixed forest types, in terms of both species and age classes, are advocated. In addition, natural or imitated natural regeneration is indicated as a method of maintaining genetic diversity, and subsequently reducing vulnerability. For management against extreme disturbances, improvements in fire detection and suppression techniques are recommended, as well as methods for combating pests and diseases. It is reported that through stricter quarantine and sanitary management, the impact of insects and diseases can be minimized. The establishment of migration corridors between forest reserves may aid in the autonomous colonization and migration of species in response to climate change (28).

Adaptive management

The terms adaptation and adaptive management are often incorrectly used interchangeably. The former involves making adjustments in response to or in anticipation of climate change whereas the latter describes a management system that may be considered, in itself, to be an adaptation tactic (25). Adaptive management is a systematic process for continually improving management policies and practices by learning from the outcomes of operational programmes (26). It involves recognizing uncertainty and establishing methodologies to test hypotheses concerning those uncertainties; it uses management as a tool not only to change the system but to learn about the system (27).

Both the climate and forest ecosystems are constantly changing, and managers will need to adapt their strategies as the climate evolves over the long term. An option that might be appropriate today given expected changes over the next 20 years may no longer be appropriate in 20 years’ time. This will require a continuous programme of actions, monitoring and evaluation – the adaptive management approach described above (28).

There is a widespread assumption that the forest currently at a site is adapted to the current conditions, but this ignores the extent to which the climate has changed over the past 200–300 years, and the lag effects that occur in forests. As a result, replacement of a forest by one of the same composition may no longer be a suitable strategy (28).

Adaptation to climate change has started to be incorporated into all levels of governance, from forest management to international forest policy. Often these policies are not adopted solely in response to climate, and may occur in the absence of knowledge about longer-term climate change. They often serve more than one purpose, including food and fuel provision, shelter and minimizing erosion, as well as adapting to changing climatic conditions (32).

Socio-economic and political conditions have significant influences on vulnerability and adaptive capacity. Climate change projections are perceived by many forest managers as too uncertain to support long-term and potentially costly decisions that may be difficult to reverse. Similarly, uncertainty over future policy developments may also constrain action. Finance is a further barrier to implementing adaptation actions in the forest sector (33).

References

The references below are cited in full in a separate map 'References'. Please click here if you are looking for the full references for the United Kingdom.

1. Department of Energy and Climate Change of the United Kingdom (2009)
2. Holman et al. (2002)
3. Land Use Consultants, CAG Consultants and SQW Limited (2003b)
4. Kerr et al. (1999)
5. West and Gawith (2005)
6. C-CLIF and GEMRU (2003)
7. Kellomäki et al. (2000)
8. Walter (1979), in: Fischlin (ed.) (2009)
9. Melillo et al. (1993), in: Fischlin (ed.) (2009)
10. Reich and Frelich (2002), in: Fischlin (ed.) (2009)
11. Carrer and Urbinati (2006), in: Fischlin (ed.) (2009)
12. Field et al. (2007b), in: Fischlin (ed.) (2009)
13. Hyvönen et al. (2007); Magnani et al. (2007), both in: Fischlin (ed.) (2009)
14. Marshall et al. (2008), in: Fischlin (ed.) (2009)
15. Chmielewski and Rötzer (2001); Parmesan (2006), both in: Fischlin (ed.) (2009)
16. Alcamo et al. (2007); Field et al. (2007b); Alo and Wang (2008), all in: Fischlin (ed.) (2009)
17. Lucht et al. (2006); Scholze et al. (2006); Alo and Wang (2008), all in: Fischlin (ed.) (2009)
18. Williams et al. (2000); Williams and Liebhold (2002); Logan and Powell (2001); Tran et al. (2007); Friedenberg et al. (2008), all in: Fischlin (ed.) (2009)
19. Fischlin (ed.) (2009)
20. Iverson and Prasad (2001); Ohlemüller et al. (2006); Fischlin et al. (2007); Golubyatnikov and Denisenko (2007), all in: Fischlin (ed.) (2009)
21. Perry et al. (2008), in: Fischlin (ed.) (2009)
22. Liski et al. (2002), in: Fischlin (ed.) (2009)
23. Piao et al. (2008), in: Fischlin (ed.) (2009)
24. Morales et al. (2007), in: Fischlin (ed.) (2009)
25. Christensen et al. (2007); Fischlin et al. (2007); Meehl et al. (2007); Schneider et al. (2007), all in: Fischlin (ed.) (2009)
26. Hanson and Weltzin (2000), in: Fischlin (ed.) (2009)
27. Karjalainen et al. (2003); Nabuurs et al. (2002); Perez-Garcia et al. (2002); Sohngen et al. (2001), in: Osman-Elasha and Parrotta (2009)
28. Innes (ed.) (2009)
29. Ogden and Innes (2007), in: Innes (ed.) (2009)
30. BCMOF (2006a), in: Innes (ed.) (2009)
31. Holling (1978); Lee (1993, 2001), all in: Innes (ed.) (2009)
32. Roberts (ed.) (2009)
33. Keskitalo (2008), in: Roberts (ed.) (2009)
34. Kirilenko and Sedjo (2007)
35. Boisvenue et al. (2006)
36. Schelhaas et al. (2010)
37. Li et al. (2016)
38. Evans and Warburton (2007), in: Li et al. (2016)
39. Tallis (1998), in: Li et al. (2016)
40. Labadz et al. (1991); Pattinson et al. (1994); Rothwell et al. (2005, 2007); Ramchunder et al. (2009); Grayson et al. (2012); Pawson et al. (2012), all in: Li et al. (2016)
41. Parry et al. (2014), in: Li et al. (2016)