Over the last few years, it has seemed like the idea of planting trees to fight climate change has been gaining in popularity, particularly among those who want to avoid any real systemic change. I also have a sneaking suspicion that if they do get around to any tree-planting, their goal will be to plant large numbers of whatever is cheapest. Unfortunately, if you’re trying to actually help an ecosystem recover, that’s very slow, inefficient way to go about it. It’s depressingly clear that some people will never accept this message, but diversity really is better:
One of the world’s biggest ecological experiments, co-led by the University of Oxford on the island of Borneo, has revealed that replanting logged tropical forests with diverse mixtures of seedlings can significantly accelerate their recovery. The findings, published today in the journal Science Advances, emphasise the importance of preserving biodiversity in pristine forests and restoring it in recovering logged forest.
The experiment was set up by the University of Oxford’s Professor Andy Hector and colleagues over 20 years ago, as part of the SE Asia Rainforest Research Partnership (SEARRP). This assessed the recovery of 125 different plots in an area of logged tropical forest that were sown with different combinations of tree species. The results revealed plots replanted with a mixture of 16 native tree species showed faster recovery of canopy area and total tree biomass, compared to plots replanted with four or just one species. However, even plots that had been replanted with one tree species, were recovering more quickly than those left to restore naturally.
Professor Hector, the lead scientist of the study, said, ‘Our new study demonstrates that replanting logged tropical forests with diverse mixtures of native tree species achieves multiple wins, accelerating the restoration of tree cover, biodiversity, and important ecosystem services such as carbon sequestration.’
According to the researchers, a likely reason behind the result is that different tree species occupy different positions, or ‘niches’, within an ecosystem. This includes both the physical and environmental conditions to which the species is adapted, and how it interacts with other organisms. As a result, diverse mixtures complement each other to increase overall functioning and stability of the ecosystem. For instance, some tropical tree species are more tolerant of drought because they produce a greater amount of protective chemicals, giving the forest resilience to periodic times of low rainfall. Professor Hector added, ‘Having diversity in a tropical forest can be likened to an insurance effect, similar to having a financial strategy of diverse investment portfolios.’
Well, putting it in financial terms does seem like one way to get them to see the value of diversity. Well played, Professor Hector.
Beyond reinforcing what ecologists have long known about the importance of biodiversity, this study shows that we absolutely can intervene to help ecosystems recover more quickly. Doing so is not going to be enough by itself – we need to end fossil fuel use or it’s pointless – but in addition to having the tools to do that, we also have the tools to make real progress on repairing the damage we’ve done to the world’s ecosystems. Unfortunately, we can’t really get to work on that until we stop doing that damage in the first place. No amount of forest restoration work will help us, if old forests are still being destroyed to make way for oil palm plantations.
Things like this are why I think systemic change is necessary – because our system is set up in such a way that it can’t really promote or protect things that don’t have a monetary value. We know that we need healthy forests, for our own sake, but we keep destroying them anyway, and restoration is generally more of an afterthought. I suppose if I’m keeping to the theme of this post, then I would say that we need to “diversify” our political and economic systems, so that they can allow for healthy ecosystems, human flourishing, and progress, without all the destructive overproduction.