effect via both shade and evapotranspiration (the movement of water into the atmosphere, some of which comes through leaves).
Large trees are unequalled in cooling the environment around them. Old trees simply do things on a scale that small young trees cannot.
This means a slow-growing old tree can take in and store more carbon than a quick-growing young seedling. Every gram of carbon stored in this way is carbon saved from going into the atmosphere as greenhouse gas emissions.
Both carbon stores and shade are crucial to mitigating future climate change.
All of this is lost when trees are illegally or unnecessarily removed. The impact is felt not just now but for decades into the future.
The loss of even a single tree comes at a huge priceThe loss of so many trees in Sydney’s Castle Cove represents theft of environmental benefits and services from at least two, if not more, future generations of Australians. The trees lost were largely native coastal species that had decades (and in some cases more than a century) of growth before them.
We have known for many decades trees are often associated with between 30 and 50 other species – birds, mammals, reptiles, insects, fungi, algae and others. The removal of a tree affects most, if not all, of these other species. Some of these plants and animals will die as a result.
The number of associated species increases as the tree ages, and we have probably been underestimating species lost with large old tree removals in urban and natural forests.
Oaks in the UK, for example, are associated with over 2,300 other species. One can only wonder how many other species will be affected by the felling and poisoning of the trees at Castle Cove. The illegal loss of even a single tree comes at a huge price.
Simply planting new trees doesn’t fix the problemWe tend to undervalue the shade provided by trees when considering urban development, or even road works. But tree removals lead to more urban heat, which usually means higher electricity bills (as people crank up the air conditioner).
Large old trees are seen by some as an expendable nuisance. Some local council laws aim to protect trees of a certain size, but fines for illegal removals are small.
In some instances, a one-for-one tree replacement is offered. But to replace the carbon stored in one large, mature tree would require a vast number of seedlings, many of which fail to survive the first few years.
And it can take many years before planted trees reach carbon neutrality. The production, planting and maintenance processes all use resources, energy and fossil fuels, which means it can take decades before a tree is carbon positive.
This situation is unsustainable environmentally and ludicrous economically, but it seems to go largely unnoticed. We accrue all of the costs of these plantings and recoup precious little benefit.
It would be far more sensible and sustainable if we retained our large old trees, making every effort to maximise and prolong their life spans.
Bushwalk
