Why are trees climate warriors?
KCC spoke with Howell Davies from Auckland City Council and
NZArb to answer this question...
The ultimate carbon capture and storage machines
Trees are great carbon sinks. They absorb atmospheric carbon (CO2) – one of the main greenhouse gases – and they are so good at this that they lock it up for centuries. It stays in their living wood, deadwood, roots, leaves, and surrounding soil.
Trees do this as they churn through photosynthesis. This is the process where trees use sunlight, water, and carbon dioxide to create oxygen and their own energy. Trees are feeding themselves with the carbon we desperately need to avoid getting into the atmosphere!
How can we help? More trees are needed to do this essential work. All trees are great, but we can help most by planting longer lived hardwood trees, especially natives, like pōhutukawa, tōtara, kauri, NZ beech, matai, puketea, and maire. It’s important the trees we plant are suited to where we live too.
Our battle-hardened Carbon Capture and Storage Machines are our big, old trees. The bigger the tree the bigger the benefit they can make! We need to look after them just as much as we need to plant more trees – if not more.
Trees are amazing at making air, but also cleaning it. They are a bit like our liver in that way. When they take in pollution, they filter it through their leaves, so it will stay in their wood, bark, leaves, and needles and not be released back into the atmosphere.
Air pollution affects how much sunlight is being reflected (bounced back) or absorbed (taken in) by our atmosphere. In urban areas, trees are particularly good at trapping particulates from our car exhausts.
But we are making too much pollution, and too many greenhouse gases, and it is messing with the way trees do this job (and many other interconnected environmental systems).
To help our Pollution Reducers, we can think carefully and make changes around how we use energy and transport, and what types we use too.
Trees shape themselves to the weather where they live over their long lives. For instance, most NZ trees have built up strong oblong shaped branches, rather than round ones. Some trees have a lean, or unusual shapes to their foliage (leaves) as they have responded to the wind.
Trees know how to stand up to our weather, and to work with it, and it is a good thing they do.
With climate change, some areas of Aotearoa are getting more rain, for longer. Our trees are working like protective umbrellas, helping to reduce rain impact on the ground during storms (i.e. less flooding). In urban areas, this is particularly important as it also helps keep stormwater and wastewater systems working well.
But with climate change too, weather is becoming random, and the conditions are changing too fast, and some trees cannot keep up. For instance, we are seeing trees fall down with storms because one too many extreme gusts coming from a different direction than normal. We may not be able to grow trees that are used to colder climates, such as oak, in Auckland in 50 years time. The winter season has become not as long as it used to be.
We can help our Weather Battlers deal better with extreme weather, and to adjust better to fast change by checking in on them regularly, watering in times of drought*, and keeping them and their roots healthy (e.g., by doing pruning, weeding, or predator control).
* Check out Cooling Shields for more on how to help trees handle extreme heat.
During the day, trees provide shade that helps to block the hot rays of the sun, but night time is where the real magic happens.
At night, trees transpire. This is the process by which water is carried up through the tree from the roots to the small pores on the underside of leaves. Once the water gets to the leaves, it is turned into vapor (like a mist) which then gets released out into our atmosphere. The water vapor cools down the whole area around where the trees live. Cool huh?
As climate change is raising temperatures throughout the motu, we need our trees functioning at their very best, but they too are affected by the heat. When it gets hotter than 34 °C, photosynthesis slows down, and trees start to run out of energy.
To help our Cooling Shields during heatwaves, we can water them, spread mulch, and create shade for them too. A tip – grey water from the shower and washing machines is fine to use on trees and is a sustainable option.
Trees are like wine glasses. They have fine stems (trunks) but very broad bases (their network of roots). Tree roots go out metres past where the trees stand. Like a net, these roots keep the soil around them all bound together. The roots keep growing and moving around to make the soil even more secure for them too (if they didn’t, they would fall over!). This is amazing for stopping soil erosion – that is, where soil is washed or blown away.
We need our soil to stay put so the land can capture carbon and grow carbon-sucking plants.
Help our Cargo Nets by giving them the room they need for their roots to grow and take hold.
Soil Enrichers and Biodiversity Supporters
Climate change is messing with our ecosystems (for instance, helping pests – including weeds – and predators get into new areas, and/or in bigger numbers), yet healthy ecosystems are needed for a healthy world.
Trees to the rescue!
Trees are protecting and feeding the soil around them with their leaf litter. They are attracting all sorts of amazing bugs, microorganisms and fungi that do an amazing job of enriching the soil too with their activities. Trees support habitats of amazing native plant and animal species and are themselves a habitat for many.
Help our Soil Enrichers and Biodiversity Supporters by doing and supporting pest and predator control.
Did you know Auckland is a tree city of the world? Check out all the benefits of trees!
Arborists are tree experts and know the best methods and techniques for keeping trees happy and healthy. Use the NZArb website to help you find an arborist: https://www.nzarb.org.nz/find-an-arborist