For millions of years, forests and woodlands have been changing - as a result of natural regeneration, storms, fires and climate change.  However, with the expansion of human populations, woodlands and forests have been cut down to make way for towns, cities and the infra-structure of ‘modern’ life.  Sadly forests, and woodlands such as those in the path of HS2,  are still disappearing. ‘Untouched’ rain / tropical forest is being cut down to make way for cash crops; plus vast wooded areas have been destroyed by fire in Australia, Sweden and on the West Coast of the United States in recent years. Clearfell of any forested area for timber or agriculture involves the removal of all trees / vegetation and is sometimes followed by burning of the remaining debris. Clearfell can also have unintended consequences (beyond the loss of entire animal communities.  An Australian study has shown that it lowers soil nutrient levels - notably nitrate and phosphate.  Furthermore, the use of heavy machinery in clearfelling can compact the soil and its consequent exposure to the elements can lead to erosion (rain runoff).   When an area is subject to intense fire, there is a drop in the organic carbon content of the soil and structural damage to the soil; it can take many years for such fire-damaged soil to ‘recover’. Forests and woodlands support the vast majority of land-based species. However,  the species that we see today on a woodland walk may be different to those our ancestors might have seen five hundred or a thousand years ago.  Certain species only survive in relatively undisturbed (and ancient) forests / woodlands.  There are species that can ‘deal’ with disturbance and are adaptable, indeed opportunitistic,  such as red deer and fox.  The same can be said for certain plants species, which can become invasive.   Changes in species make-up and biodiversity do not always immediately follow loss of forest or woodland.  Generally speaking, the longer the life span of a species then the longer for the effects of forest loss to become apparent.  It may be that the effects ‘span’ generations, raptors / birds of prey may manage to raise their young in the immediate period following loss of forest or woodland. But their offspring may struggle to survive in a depleted environment. It might be that with limited resources an animal might simply not reproduce for years, if ever again.  Consequently, the impact of forest destruction / loss that species depletion might not be apparent for many years. The loss of forests and woodlands has lead to many local, national and inter-national initiatives to offset these losses: for example, New Zealand’s ‘One Billion Trees” project and the Nature Conservancy’s “plant a billion trees’ campaign.  Broadly speaking, reforestation involves the planting of native trees in an area, whereas planting with new (non-native) species is afforestation. Recent research suggests that whilst non-native plants often grow faster than native species, they also have less dense tissues (think: oak versus larch) and decompose more readily, which can contribute to more rapid cycling of carbon.  This will not help to mitigate climate change. It is also important to consider which trees might prosper and offer resilience in the light of climate change. Our climate is changing and will be different in the future, with summer temperatures being higher.  We have already seen more extreme weather events (leading to flooding and wild fires).  Forestry England has a number of tools to help plan which tree species will be suited to a site, now and in future.   There is ESC4 which offers a means to help forest managers and planners select tree species that are ecologically suited to particular sites; and there is also the climate matching tool.  As Forestry England says this is “so that we can see which places in the world currently experience the climate we are projected to have in future. We can compare these different places to help us plan which tree species will be suited to a site, now and in future”.  One strategy is to create woodlands that are more diverse, as it thought that diversity helps woods more resilient to climate change. This can be through encouraging a range of different, but carefully selected trees to grow, and being aware of the provenance of seeds or saplings.

Certain upland areas of the UK , such as Dartmoor, have experienced long term grazing.  This has lead to soil compaction, which in turn means that water run-off is greater. Instead of percolating into the soil, rain water runs over the surface and into rivers. This can lead to flooding during extreme weather events.   Dartmoor (National Park) is a large upland area, which historically was dominated by oak woodland.  Oak woodland now covers a very small area.   The region is now dominated by blanket bog, heathland and acid grassland.  The number of grazing animals (sheep, cattle and ponies - deer) increased significantly between the 1950s and 2000, resulting in soil compaction. Researchers at the University of Plymouth have investigated areas of upland pasture on Dartmoor, and the potential for the establishment of native oak saplings. Working with test sites, they were able to show that significant improvements in soil properties could be observed with 15 years of sapling establishment.   The most effective location (in terms of flood prevention) for sapling / tree planting was on steep hillside on the edge of upland areas.   Their initial work on the planting of woodland has since been expanded to determine the factors that affect the establishment of the tree (oak) saplings.  Their most recent paper notes that the presence of livestock meant that fewer oak saplings survived and those that did were smaller.  However, the effects of cattle and ponies was not always negative in that their trampling could reduce the growth of bracken - allowing more light to reach young tree saplings. [caption id="attachment_34391" align="aligncenter" width="650"] A southern upload moorland - Exmoor[/caption] The research team formulated a number of recommendations relating to the creation / establishment of woodlands in such upland pastures. Livestock should be excluded in areas where there are seedlings and young saplings (1 - 3 years). This exclusion should last for some 12 years. Larger oak (4 - 7 yrs) saplings can be planted into areas of dense vegetation, as this protects the saplings from livestock. Livestock could be allowed to graze in the vicinity of mature oak trees as this would reduce dense, competitive vegetation, allowing seedlings to grow / develop.  Strategic planting and management should be considered  / encouraged for upland slopes where drainage is poor - to allow for soil recovery and development of ecosystem services (flood mitigation). Whilst natural tree colonisation is a low-cost and environmentally sensitive mechanism to promote woodland expansion (working towards government targets on climate mitigation, carbon sequestration etc.), it is likely that the expansion of oak woodland into upland pasture systems will require strategic planting and informed livestock management. [caption id="attachment_37920" align="aligncenter" width="650"] Exmoor Ponies.[/caption] Full details of their paper can be found here : https://besjournals.onlinelibrary.wiley.com/doi/10.1002/2688-8319.12126  (Thanks to Art for images of exmoor and ponies).

We tend not to think about soil very much, except perhaps when digging over a tough patch of weeds in the garden or if we see it being stripped from dry fields in a strong wind.  We take soil for granted though we rely on it for our food - almost totally.  Soil is a very thin layer covering the outer surface of the Earth.  The earth’s crust varies in thickness from 3 miles in oceanic regions to 30 miles in continental areas - by comparison most soils are shallow and have little depth. Sadly, the earth’s soils have been neglected and squandered throughout history.  In America and Canada, deep ploughing of the prairies and subsequent drought left the ‘unanchored soil’ exposed to wind erosion. Read more...

With the changing nature of our climate, so extreme events have become more frequent.  The last fifteen or so years has seen significant episodes of flooding.  Flooding used to be a relatively unusual event in the U.K.   In consequence,  efforts are now being directed at finding ways of mitigating the effects of extreme rainfall. The risk of flooding is associated with changes in our climate (notably rainfall patterns) and the techniques of land management have changed with the mechanisation of agriculture,  the creation of simplified (larger) field systems, land drainage, increased stock densities etc.  The U.K. landscape / countryside has altered significantly over the last fifty years.   Read more...

In 1987, the U.K. was battered by a storm – said to have been the worst that this country has experienced in three hundred years.  Hurricane force winds raged across southern England and the Midlands before the storm finally exited via the Wash.  It is often referred to as “The Great Storm” Millions of trees were uprooted, woodlands flattened, parks and gardens destroyed, the National Grid damaged, cars hit by falling branches and people died.  Places like Wakehurst Place, the Sussex outpost of the Royal Botanic Gardens (Kew) lost some 60% of their tree collection as a result of this storm.  Kew Gardens itself lost many trees.  Many were uprooted and died. Read more...