Thanks to Greta Thunberg and her global youth climate movement, it seems everywhere you look these days people are talking about climate change - and about time too!
As people are slowly starting to sit up and pay attention to what is arguably the most pressing issue of our time, our best minds have been put hard to work engineering climate solutions. From designing ways to capture and store carbon deep underground, to pumping our skies full of sulphur, most of these proposed solutions are at best costly, and at worst incredibly environmentally damaging.
But something that's not been spoken so much about is the enormous potential that trees and, more specifically, agroforestry, hold in combatting climate change. Low-tech, cheap and sustainable, it is becoming increasingly evident that natural climate solutions, through the use of afforestation and alternative agricultural practices, are some of the most efficient ways to fight climate change, with some scientists even arguing that these should be prioritised over other climate change efforts. Maybe people are wondering right now, what is agroforestry so a link or something? Maybe youre targeting people that know already?
In our current climate situation, a trick like this is something we simply cannot afford to miss. So how does agroforestry help in carbon sequestration?
As a quick overview, carbon (in the form of carbon dioxide) is one of the most important greenhouse gases contributing to climate change. The more of these gases in our atmosphere, the warmer it gets and, thanks to a combination of our love of burning carbon-based fuels and rampant deforestation, there is no question that carbon is rising in our atmosphere at an alarming rate – at a rate of around 4.3 billion tonnes per year, to be more precise.
Carbon is not an inherently bad thing- in fact, it's something that our system needs to function and is already cycling in our atmosphere and through all living things, like trees, as it has been for thousands of years.
However, our system works only when all components are in a very delicate balance. It only takes a slight tip of the scales for things to go awry, but unfortunately those scales are starting to become way off balance.
Our Best Tree-source
Trees are the original, and ultimate, carbon storage machines.
As with other plants, trees take up carbon dioxide during photosynthesis and use molecules of carbon to create their physical structures. In fact, it’s estimated that the average dry weight of a tree is about 50% carbon which they store over their lifetimes which can mean hundreds, sometimes even thousands, of years.
And it gets better. As well as locking up carbon, trees also create carbon-rich ecosystems which in turn store carbon. When their leaves fall off and their fine roots die off, they become carbon-rich organic matter in and on top of soil. Furthermore, by releasing ‘exudates’ (a fancy way of saying certain liquids, often sugary substances) from their roots, trees also cultivate their own microbial environment around their root zone, encouraging organisms who then in turn store carbon.
What's more, it's important to understand that not all carbon is made equal. By this, I mean that it has been shown that the carbon in soils under forest cover is in a more stable form than commonly found elsewhere, meaning carbon in those soils is less likely to be released back into the atmosphere.
Tree-mendous Carbon Storing Potential
A quick google search is enough to see how complicated it is to get a straight answer for how much carbon trees sequester. So many factors, such as soil type, environmental conditions, and tree variety, influence the amount of carbon a tree can sequester.
That being said, there is more and more research coming out calculating the carbon sequestration potential of trees.
The “Trees for the Future’s Forest Garden program” has estimated that the average hectare of forest sequesters 62.8 metric tons of carbon, which equates to an average carbon offset of nearly 16kg per tree.
To put this in context a bit, the average flights produces 250kg of carbon per hour and the average car emits about 4.6 metric tonnes of carbon per year. This might seem a lot - and that’s because it is.
But with initiatives already launched such as the ambitious Trillion Trees project aiming to restore one trillion trees by mid-century, you can see how trees hold enormous potential to combat our carbon hungry lifestyles.
Agroforestry and Climate Smart Agriculture
To sum up, trees are great. But as great as trees are, forests are better.
And that is an important distinction to make. It means that, as great as it is to incorporate trees into traditional agricultural systems or to plant individual trees, for trees to be at their most efficient, maximum carbon storage potential, they have to be in a system with other trees. And that's where agroforestry comes in.
But why would this be? Well, one thing is that diversity is key to ecosystem health. A recent study looking at the carbon storage of forests in southern China found that each additional tree species introduced to a plantation could add 6% to its total carbon stocks, and that forests containing several tree species could store twice as much carbon as the average monoculture plantation. Agroforestry, working to incorporate a diverse polyculture of crops and species, therefore has much more potential to store more carbon than conventional cropping systems.
Furthermore, it's becoming increasingly clear that it's not just trees that are important for carbon storage, but also the soil that lies beneath which actually holds the most carbon storage potential. The Earth's soils are one of our biggest reservoirs of carbon, holding over four times the amount of carbon locked up in trees and plants, and nearly three times the carbon contained in the atmosphere.
However, soil carbon is extremely sensitive to land use and agricultural practices such as tilling (see our blog for more details) and the extensive use of chemical fertilisers works both to damage the soil and release a huge amount of carbon into our atmosphere.
However, agroforestry systems, through the intelligent incorporation of tree systems and ecological techniques such as using support species, mulching and tree stratification, reduce the need to till, thus sequestering carbon both above and belowground.
And let’s not forget about our fungi friends who, thanks to a no-till system, are able to flourish in the soil and provide a huge contribution to carbon sequestration (so huge, in fact, that recent evidence suggests that fungi in boreal forests actually sequester more carbon than the trees - see our blog for more details). Moreover, that fungi play a key role in carbon sequestration.
The “4 per 1000” initiative, which advocates agroforestry as a climate change solution, estimates that an annual growth rate of just 0.4% in the soil carbon in the first 30-40 cm of soil would significantly reduce the CO2 concentration in the atmosphere related to human activities.
A More Tree-freshing Look at Climate Change
It's often pretty doom and gloom talking about climate change. But trees, and the power of agroforestry, provides a tree-freshing approach to tackling our biggest environmental issue.
So I’d say it’s high time we put the carbon back in the soil where it belongs!
Thanks for reading,