The True Value Of Trees

A tree’s value is not just aesthetic or sentimental; it is so much more.

Cast your mind back to the recent hot spell of weather we had this summer, and the benefits trees brought in the form of providing shelter from the hot sun.

Most cities and towns sizzled with temperatures exceeding 30C and with global warming set to continue, we are likely to see more periods of hot weather in the coming years. Cities get particularly hot during the summer due to the urban heat island effect which is caused by hard surfaces, like roads and buildings, absorbing heat from the sun.

However, new research has shown trees can cool cities down by as much as 5C. The trees we plant now, or the areas we pave now, are going to be determining the temperatures of our cities in the next century.

Although a single tree can provide partial relief from hot summer sun, when there are many of them together it has a profound cooling effect. Scientists found that 40% tree cover cools streets more than the pavement warm them up.

The effects of climate change are already being felt. We’re experiencing warmer, wetter winters, and hotter, drier summers, creating higher temperatures in our cities. Climate change has caused an increase in pests and disease, which had never previously affected the UK. The impact has been an unprecedented threat to some iconic tree species, including ash, horse chestnut and oak.

By planting thousands of urban trees worldwide each year, the group Trees for Cities are building resilience against threats facing the natural environment.  Planting a range of tree species enhances structural and functional diversity in woodlands and on city streets, as well as building resistance to pests and disease.

Trees are one of the most valuable assets in any community, yet I would argue that they are also among the most undervalued and overlooked resources in our towns, villages, cities and public parks.

We often look at a tree and see something that needs pruning, leaf clearance, maintenance or eventually replacement. But we should be looking at it as a living piece of community infrastructure that delivers enormous environmental, social, economic and health benefits.

A mature tree is not simply a piece of landscaping. It is a natural asset that provides services to society every single day, often without the public appreciating its true worth.

There are several important ways in which we should measure that value.

Trees make a substantial contribution to improving the environment in which we live.

• Carbon sequestration: Trees absorb carbon dioxide as they grow and store carbon in their trunks, branches, roots and surrounding soils.
• Air quality: Leaves can capture particulate pollution, and trees can intercept some airborne pollutants.
• Temperature regulation: Tree canopies provide shade and cool the surrounding environment through evapotranspiration.
• Flood prevention: Trees intercept rainfall, improve soil structure and help reduce surface-water runoff.
• Biodiversity: They provide food, shelter and nesting sites for birds, insects, bats and other wildlife.
• Wind protection: Trees can reduce wind speeds and create more sheltered public spaces.

There is also an important social dimension. Well-maintained tree-lined parks and streets create places where people feel comfortable, safe and connected to their neighbourhood.

I believe we need to change the way society views its trees. For too long, trees have sometimes been regarded as an expense within local authority parks and grounds maintenance budgets, rather than an investment in the future health and wellbeing of our communities.

We spend millions of pounds maintaining roads, drainage systems, buildings and other public infrastructure. Yet the trees that help cool our streets, absorb rainfall, improve our surroundings and support wildlife often struggle to receive the same recognition and long-term investment.

We should be asking not how much it costs to maintain our community trees, but how much it would cost our communities if we lost them.

A tree planted today is an investment for generations to come. A mature tree protected today is an asset that our children and grandchildren can continue to enjoy.

Just look at the current vibrant autumn leaf colour we are currently seeing, which singles the end of the growing season with many deciduous trees losing their leaves ready for the winter.

This time of the year, November also singles the start of the tree planting season.

 Why do we plant trees in the winter?

Winter is traditionally the best time to plant many trees in the UK, particularly deciduous trees supplied as bare-root stock. There are sound horticultural and scientific reasons for this, principally relating to the tree’s dormant period, soil moisture, root establishment and reduced transplanting stress.

Winter planting gives trees an opportunity to establish their root systems before the demands of spring and summer growth begin.

One of the main reasons for winter planting is that most deciduous trees enter a period of dormancy during autumn and winter.

• Leaves have fallen, reducing water loss through transpiration.
• Shoot and leaf growth has largely stopped.
• Energy reserves are stored in the roots, trunk and branches.
• The tree’s water requirements are considerably lower.
• Transplanting causes less disruption to active above-ground growth.

This means the tree can be lifted, transported and replanted with less physiological stress than during the growing season.

The UK generally experiences higher rainfall and lower evaporation during the winter months. This provides several advantages, soil moisture is more readily available, newly planted trees are less likely to experience any immediate drought stress, and soil moisture helps maintain good contact between roots and surrounding soil.

However, planting into saturated, waterlogged or frozen ground should be avoided because this can damage soil structure and compromise establishment.

So, if there is one valuable job to do this winter, it will be to consider planting some trees that in the future will give us the pleasure we can see today from the valuable tree planting of the Victorians. In particular, the vision of Capability Brown whose tree planting and garden designs in the 18^th Century we are still benefitting from.

Brown’s style came from the three practical principles of comfort, economy and elegance. He designed landscapes on an immense scale, which provided a setting for mansions which were surrounded by woodland, parkland dotted with trees and carefully contoured ground. His landscapes also incorporated serpentine shaped lakes and carefully designed architectural features including follies are seen today in the many country houses and national trust properties we visit today.