Woodland Management and Climate Change
One of the main overall objectives of woodland management for the UK government and most countries around the world is to improve habitat for biodiversity, as established at the Rio Convention on Biological Diversity in 1992. For Essex County Council as well, this is a prime driver for managing woodland.
Unmanaged woodland blocks are typically dark under the canopy, where little in the way of flora, tree or shrub regeneration and understorey can exist. This environment is not used for nesting by birds, which generally prefer a more shrubby, open habitat with warmth, protection and some light, or by other valued native species.
Creating the right conditions means letting in light by felling trees. Marking trees for felling is done with a number of objectives in mind. General aims are to have a healthy, resilient woodland with a diversity of species, ages and heights, with some gaps, potentially for natural regeneration or planting. Veteran trees are “halo thinned”, to give enough light for their crowns not to be out-competed by surrounding trees. Some species such as oak are favoured over others for the future structure of the woodland, so these are given space, ie there is a judicious marking of trees around them. If there is a general uniform matrix as though it is a planted crop, this is thinned not so much to give space to retained trees to grow on to a final harvest, at which point there would be a rather shocking clear fell, but to create and sustain a lighter canopy.
As a procedure, marking is done by focussing on the arrangement and competition of crowns in the high canopy, as well as needs of veterans, woodland health, long term stability and ventilation, species choice, composition, shading of some stems and many other objectives.
The concept of woodland resilience to climate change addresses how a new and extreme climate will affect the various species our woodlands are composed of. Different tree species will tolerate change in different ways, ranging possibly from benefitting from some changes to dying out. Episodes of drought, heat stress and continual standing water are likely, as well as increasing carbon dioxide and other nutrients in the atmosphere, which are likely to increase vulnerability to existing or new diseases. Coppicing or creating regeneration gaps in a thinning provides opportunity for rejuvenation and increasing species diversity within blocks, by enabling natural regeneration and supplementary planting.
This felling produces a lot of timber.
With a new awareness of climate change, some might think it is better to consider trees as a way of storing carbon, and that felling them will release this carbon into the atmosphere. However, given the above objectives and benefits to biodiversity, there are also other positive outcomes to consider: