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Introduction
Concern
about the impacts of climate change on our trees and
woodlands has led to increasing interest from owners
and managers. The science of climate change and tree-related
research is developing fast but advice for landowners
can be difficult to access or remains unclear. This
publication sets out to summarise the science and provide
advice for future-proof woodland management.
What
do we want from our woodlands in the 21st Century?
Trees,
woods and forests are important for society, the economy
and the environment. They are the single largest natural
land-type supporting biodiversity in Europe. As climate
change increasingly affects our lives, our woodlands
are likely to be ever more important in providing ecoservices
(such as landscape connectivity, soil and water conservation,
habitat for wildlife) and as a carbon-lean resource
(such as wood for construction, material for bioenergy).
Long-term
forecasts in world timber trends suggest a continuing
decrease in hardwood exports from tropical forests and
increasing consumption of timber in industrialising
countries such as China and India. There are therefore
good opportunities for increasing our domestic timber
supply, particularly for valuable hardwood timbers.
This would bring many benefits, such as using timber
for use in material substitution, thereby reducing our
carbon footprint.
In
recent decades UK forest policy has concentrated on
environment and social objectives. Sustainable forest
management (SFM) must include economic factors, and
naturally, economics often drives the ambitions and
interest for woodland owners. Quality timber production
can fulfil roles in increasing domestic timber supply,
contributing by-products to bioenergy demand, and by
providing materials for product substitution. True SFM
should deliver wood products whilst protecting/enhancing
the environment and providing benefits to society.
We should aim for the best quality and health in our
woodlands. This will provide resources for the widest
range of future opportunities, including timber. In
summary – remember the mantra “quality sells”.
 Evidence
Climate
change is widely accepted as a fact. The science of
climate change is conducted and summarised at a global
level by the Intergovernmental Panel on Climate Change
(IPCC). The IPCC includes hundreds of leading experts
and therefore it seems irrational to dismiss lightly
any of their conclusions (Table 1, left).
Effects of temperature increases have been documented
(with ‘medium confidence’) on agricultural
and forestry management at Northern Hemisphere higher
latitudes. These include earlier spring planting of
crops, and alterations in natural disturbance regimes
of forests (i.e. fires and pests).
Climate
change is already affecting living systems globally,
and affecting the range and abundance of animals and
plants (Parmesan, 2006). Wide ranging evidence exists
for climate change affecting biomes, forests and tree
species across Europe
Projections
Woodland
growth will be impacted by climate change to different
degrees across Europe, the UK generally less impacted
than boreal and Mediterranean regions. The most widely
recognised impact will arise from temperature change
(warming), which will profoundly affect trees and woodlands
by altering photosynthesis and respiration, and other
factors such as phenology (e.g. leafing dates) and evolution.
 A
warming of up to 2°C may be beneficial for trees
but the response will vary between different species
(Saxe et al., 2001). Increases in CO2 (a greenhouse
gas) may also increase growth rates in the short term
(i.e. before other negative effects impact). The greatest
impact may come from extreme and unpredictable events;
so called ‘stochastic’ events, such as drought,
extreme wind and precipitation, frost, fire, insects
and pathogens. Of course, impacts are likely to come
from more than one direction and may be related. For
instance, trees stressed by drought will become more
susceptible to disease and pests.
In
the UK, we lead the world in climate science and have
a wealth of information on likely impacts of climate
change on our woodlands (e.g. Broadmeadow, 2002). Generally,
native broadleaved species may become unsuitable for
timber production on some soils and aspects. Species
projections have been developed by Forest Research following
likely scenarios for 2050 and 2080 (Broadmeadow
et al., 2005). The strongest projection is that
beech will become less viable on southern slopes in
southern England. General risks and responses are summarised
in Table 2, below.
UK
policy
 Before
deciding what you would like to do, it is important
to review the policies relating to forestry in the UK
and how they affect woodland owners and managers.
Beyond
the woodland grant schemes the key policy to highlight
here is that which relates to what tree material you
may include in a new planting scheme. The Forestry Commission
has advocated local planting material through the definition
of seed zones (Herbert et al., 1999). However,
a recent publication by Forestry Research (Hubert and
Cottrell, 2007) states that “this relatively fine-scale
system of zonation, if rigorously imposed to control
the use of planting material, may be overly restrictive
in the face of predicted climate change.” This
has yet to be reflected in any change in planting grant
schemes.
 The
recent revision of the forestry strategy for England
(Department for Environment Food and Rural Affairs,
2007) recognises the value of timber production but
perhaps falls short of recognising the reality for individual
woodland owner’s needs. We live and operate in
fast-changing times, and clearly forestry is already
moving up the rural agenda, and may benefit in the future
from increased interest and support from Government.
What
to Plant
 A
common phrase of leading climate change researchers
in recent times is ‘robustness’, or in other
words creating a resource that can resist or adapt to
change.
An
important recommendation is to avoid single species
plantations and the planting of material of narrow genetic
origin. You would be well advised not only to plant
native trees that are of local origin but also include
some sourced from further afield, ideally from further
south where our climate may be matched in the future.
Furthermore if appropriate to the site, it may also
mean that you could include some non-native trees that
are predicted to grow well with climate change (see
Table 3, right). Trees closely related to native
species (e.g. Fraxinus angustifolia.) or those
native to Europe (e.g. Juglans regia) may be
more politically acceptable in the short-term. Nothofagus
spp. may have potential but provenance choice will be
critically important.
Another
important consideration may be to use mixtures in designing
new woodlands, including different species for specific
purposes such as soil moisture retention, nitrogen fertilising
effects, wind protection and microclimate provision.
A high shrub content as part of the mixture can be highly
effective in many of these criteria.
Finally, plant with an eye to the future. What is the
purpose of the planting or what might its value be in
the future? A poorly designed plantation with poor quality
planting stock is unlikely to deliver much value.
 Where
to Plant
We
expect that stressed trees will be more susceptible
to pests and diseases, and of course will not grow or
yield well. It may be more important now than ever to
match a species carefully to the site, particularly
at the small scale. In other words, avoid planting beech
on southern facing slopes and hill tops. Best growth
for productive species such as ash and walnut will be
where there is good soil moisture and microclimate,
such as near the valley bottom or lower slopes.
At
the large scale, you might want to avoid planting beech
in the southern counties, except on the very best sites.
Conversely the suitable range of walnut and sweet chestnut
may extend north in the UK, and new species (as suggested
within Table 3, above right) may be viable
in the southern counties and south west.
 How
to Manage
Variation
in woodland age and structure will also be beneficial
in the future. Silvicultural systems can be applied
where the canopy is maintained at varied levels without
clear-felling, using varied tree species and using natural
regeneration where possible. The concept of ‘close
to nature forestry’ was advocated in the 1880s
but has increasing resonance today.
In
the UK, woodland managers should be aware of a potential
increased risk of fire, particularly in southern England,
and plan and manage forests accordingly. Pests and diseases
are difficult to manage (and predict) but risks can
be diminished through good design, such as planting
trees of different genetic origin.
 Most
crucially, operate with sustainable forest management
objectives. Aim for the best timber quality, and there
will be plenty of trees of lower quality and management
(pruning and thinning) by-products for woodfuel provision.
Retention of misshaped trees and standing deadwood,
together with sensitive understorey and ride management,
will assist biodiversity to adapt to climate change.
Finally,
a well-managed wood will provide society with landscape
value and environmental protection, and if you choose,
a wonderful place for people to enjoy for pleasure or
sport.
 Summary
Our
woodlands will play a crucial role in the 21st Century.
The global trend in timber may reflect an increasing
demand for wood products. Woodlands will be important
in supporting a carbon-lean society: where material
substitution (timber replacing brick, concrete or steel),
bioenergy and management of woodlands as carbon sinks
will be high priority. The provision of ecosystem services
will become higher priority, such as helping nature
adapt to change, linking the landscape, and soil and
water protection and management.
Woodland
management must rise to meet these challenges, whilst
owners should be able to capitalise on the values from
their forests. Assisting woodlands, tree species and
wildlife to adapt to change will be challenging. There
may be a greater role for mixed-woodlands and close
to nature forestry practice, and these may provide a
more flexible and robust forest resource. The roles
of genetics and silvicultural best practice are very
important and must be considered hand-in-hand.
There
is so much uncertainty in the science of climate change
projections, and in how the environment will respond,
it is difficult and perhaps foolhardy to make firm recommendations.
However, woodland owners and managers quite rightly
want to plan for the future and need good information
and guidance where possible. It is hoped that this publication
provides some useful pointers and encourages the reader
to find out more.
 Further
Information
Broadmeadow,
M., (2002). Climate change: impacts on UK forests.
Forestry Commission Bulletin 125, Edinburgh, 119-140
pp.
Broadmeadow, M., Ray, D. and Samuel, C.,
(2005). Climate change and the future for broadleaved
tree species in Britain. Forestry, 78(2): 145-161.
Department for Environment Food and Rural Affairs,
(2007). A strategy for England’s trees, woods
and forests, www.defra.gov.uk, pp. 42.
Herbert, R., Samuel, S. and Patterson, G.,
(1999).
Using local stock for planting native trees and shrubs,
Forestry Commission Practice Note 8. Forestry Commission,
Edinburgh, pp. 8.
Hubert, J. and Cottrell, J., (2007).
The role of forest genetic resources in helping British
forests respond to climate change, Information note
June 2007, FCIN086. Forestry Commission, Edinburgh.
Kellomäki, S. and Leinonen, S.,
(2005). Management of European Forests Under Changing
Climatic Conditions. SilviStrat Final Report. Tiedonantoja/Research
Notes No. 163. University of Joensuu, Faculty of Forestry.
ISBN: 952-458-652-5. , pp. 427.
Parmesan, C., (2006). Ecological and
evolutionary responses to recent climate change. Annual
Review of Ecology, Evolution and Systematics, 37: 637-669.
Saxe, H., Cannell, M., Johnsen, Ø., Ryan,
M. and Vourlitis, G., (2001). Tree and forest
functioning in response to global warming. Tansley review
no. 123. New Phytologist, 149: 369-400.
Web
Resources
BIHP - British & Irish Hardwoods
Improvement Programme: www.bihip.org
Forest Research - The Research Agency
of the Forestry Commission: www.forestresearch.gov.uk
Forestry Horizons - A UK-based forestry
think-tank: www.forestryhorizons.eu
IPCC - The Intergovernmental Panel
on Climate Change: www.ipcc.ch
Valbro - Growing valuable broadleaved
trees: www.valbro.uni-freiburg.de
About
the Author
 Gabriel
E Hemery is Director of the independent forestry
think-tank Forestry Horizons.
He has published widely on the subjects of tree improvement,
hardwood silviculture and climate change.
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