Trees and forests are often seen as symbols of nature, and for good reason. They are very important to both the planet and humans. More than three-quarters of the world’s terrestrial biodiversity occurs in forests. Forested areas filter and manage rainwater, provide shade, absorb pollution, regulate the climate, provide oxygen, and save our souls.
About 38% of the planet’s 166,000 tree species are currently at risk of extinction due to threats from deforestation, ecosystem destruction and pests, according to an October report. evaluation From IUCN. Scientists agree that increasing Earth’s tree range would have positive benefits for the climate and ecosystems, but how to do this is complex.
In an interview with Yale Environment 360Jake M. Robinson, a researcher in restoration genomics at Flinders University in Adelaide, South Australia, spoke about how reforestation efforts, if carried out poorly, can fail, reducing biodiversity and harming local people.
“If you plant trees in an ecosystem where they shouldn’t grow, you can eliminate the biodiversity that evolved with their niche,” said Robinson, author of the recently published paper. Treewilding: Our Past, Present, and Future Relationship with Forests. “Tree planting campaigns are important, but doing them right is more important.”
Jake M. Robinson
Provided by Flinders University
Yale Environment 360: How has the planet’s tree cover changed since humans began transitioning to agricultural societies about 10,000 years ago?
Jake M. Robinson: At that time, about 45-60% of the Earth’s surface was covered with forests. That changed quickly. Our forests have grown from about 6 billion hectares to 4 billion hectares. We have lost a third of Earth’s forests over the past 10,000 years. About 50% of that loss has occurred in the last 100 years. The speed has accelerated that much since the Industrial Revolution. But the nature of the forest is also changing. Although some natural virgin forest remains, most of it is monoculture plantations.
e360: Is there a consensus on how much forest there needs to be across the planet for a healthy planet?
robinson: No, there is no agreement. Some people believe that ecosystems should be restored to how they were before human intervention. Another perspective is that ecosystem functions and processes and the biodiversity they support must be restored. It doesn’t necessarily represent the ideal that it was thousands of years ago. I would like to see us recognize that humans are part of the ecosystem and that it is okay for us to change the land. Indigenous peoples have been transforming ecosystems for tens of thousands of years.
e360: The tree planting movement has really taken off. You write that globally, planted areas have increased from 170 million hectares in 1990 to 293 million hectares in 2020. How did that happen?
robinson: This was partially promoted in 2019. science studyThis is a very controversial issue in the field of restoration ecology. They basically ran some models to show that 900 million hectares could be used to support forests, which could have about a trillion more trees. That simple idea launched into the stratosphere. The author was not advocating planting literally a trillion trees, nor was he trying to imply the absence of other essential ecosystems, such as grasslands. It was all well-intentioned and mostly just a case of poor communication.
“Restoration seems like a pretty simple idea, but… “Most ecosystem restoration projects will probably fail.”
e360: What’s wrong with the “plant a trillion trees” mentality?
robinson: Restoration seems like a pretty simple idea, but it often goes wrong. In urban areas, approximately 30% of planted trees die within the first five years. If you plant trees in an ecosystem where they shouldn’t grow, you can eliminate the biodiversity that evolved with those niches. Most ecosystem restoration projects will probably fail or fail to achieve their stated goals. There is also a big social element. This is because many people already live on the land set aside for planting trees. You may end up replacing them. Tree planting campaigns are important, but getting the right tree planting in the right place is even more important.
e360: Do you have any key examples of thoughtful and successful tree planting projects?
robinson: There is one thing I would like to note in Oaxaca, Mexico. Hundreds of years ago, there were 100,000 indigenous people supported by the local forests of Coictrahuaca, but today there are fewer than 3,000 people. The land cannot support them. Farming and poor land management have left the land so degraded. Twenty years ago the soil was essentially rocky. Local communities had to break down rocks to retain water, and then planted these small nurse species, non-native trees called Gregg’s Pines, which are well adapted to the harsh environment and do not reproduce, to stimulate the ecosystem. These trees died and their carbon was absorbed into the soil. This is an ongoing project. The ecosystem may not be thriving yet, but it just goes to show that you can start from nothing.
Pine trees were planted as part of a reforestation program in Oaxaca, Mexico.
Wolfgang Kaehler/LightRocket via Getty Images
e360: In other projects, people have a very firm preference to use only native species.
robinson: yes. In Japan, there is a technique called the Miyawaki Method. The idea is to plant a carefully selected mix of native species at very high densities to stimulate them to grow faster. This is essentially a quick way to create a functional ecosystem. However, this high density is controversial because it is artificial. Many ecologists are not fans. But in most cases, they are in urban areas with very different and novel ecosystems, and they also enjoy social benefits.
e360: The Great Green Wall initiative aims to plant swaths of trees across a vast area of tens of millions of hectares across the southern edge of the Sahara Desert. How is it going?
robinson: It was like that. [English forester] Richard St. to prevent desertification. Idea from Barbe Baker. It may be a good idea, but you have to do it right. I think they’re planting trees where they shouldn’t be and potentially a human rights issue.
e360: You talk about the concept of ‘growing’ a tree rather than ‘planting’ it. What is the difference and why does it matter?
robinson: Sometimes you just have to leave a spot and let nature do its thing. Nature will find a way and grow. But in certain situations, we have damaged the Earth so much that we need to create suitable conditions for these trees and provide them with nutrition. This is one of the challenges we are currently trying to solve. This is a method of fostering it on a large scale.
“You can tell the difference between a destroyed ecosystem and a restored ecosystem just by hearing the sound.”
e360: Of course, if we restore or plant more forests, we will have less land to grow food.
robinson: This is a big problem. I don’t use the term revolution lightly, but I believe our food system needs a revolution. Because agriculture is one of the main, if not the main, causes of ecosystem degradation on Earth.
One solution I talk about in the book is ‘syntropic agroforestry’. This is just the idea that you can produce food within a forest ecosystem and still have a thriving forest ecosystem. You need to truly understand the life cycle of trees, how to layer plants, and how communities change over time. This is what New Zealand farmer Klaus Lotz is doing. It looks very similar to a tropical rainforest. He focuses primarily on non-annual plants, including fruits and vegetables, nuts and mushrooms. He said that although yields per species are 10% lower per land area compared to monoculture systems, overall yields across all agricultural products are actually higher.
e360: You are a trained microbiologist. How important are microorganisms in forests?
robinson: It’s incredibly important. And it wasn’t thought through enough. A 5-ton tree trunk weighs approx. 1 trillion bacteria; And there are many more such as leaves, seeds, roots, flowers, etc. According to my calculations, the microbial content of wood is between 68.75 and 99.9%. It’s really amazing, right? Trees are holobionts [assemblages of a host and the many microbial species living in or around them]. Just as we now recognize the importance of the gut microbiome to human health, we must also recognize its importance to forest health.
Klaus Lotz’s “syntropic” farm in Northland, New Zealand, produces food from lush forests.
permadynamics
e360: Are foresters harnessing the power of microbes?
robinson: sometimes. Microbial inoculants are becoming increasingly popular. The idea is to create a liquid culture of microorganisms that can be sprayed on leaves or placed in the soil. [to enhance soil fertility and plant growth]Alternatively, if you are planting a tree, you can include it with a small sapling plug.
e360: I also study soil acoustics. How can you help support forest soil health?
robinson: We created small modified microphones that can be placed in the soil to detect moving animals such as earthworms, spiders, ants, and millipedes. Just as a doctor listens to a heartbeat with a stethoscope, we can tell the difference between a damaged ecosystem and a restored ecosystem just by listening. This was a really eye-opening feature and I think it will be a useful monitoring tool in the future. We also recently discovered that: white noise It can stimulate mold and promote growth. We need to figure out the evolutionary drivers of this. Why do they react? It may be ‘mistaken’ for the sound of rain, causing movement.
Climate change “is having different impacts on different forests. “Many are reducing their scope, but some are actually expanding.”
e360: How does climate change affect forests?
robinson: It has various impacts on various forests around the world. Although many forests are shrinking their extent, some are actually expanding. Along 12,000 km of the northern treeline. [where forests give way to tundra]Most of it is expanding, only a little is retreating.
e360: What are your thoughts on helping trees migrate to new climate-friendly areas?
robinson: I am working on “Climate Modified Mountains” in South Australia. We’re basically collecting seeds from a climate gradient heading north, where conditions are already warmer, and then seeing whether seeds from further afield fare better under changing conditions than seeds from local trees. We have no firm opinion on this as it is still in the experimental stage in our lab.
e360: Overall, do you think humanity is moving in the right direction to restore Earth’s forests?
robinson: I am cautiously optimistic. There are a lot of people doing really good work. We must have hope.
e360: What is the biggest, boldest step humanity can take to restore Earth’s forests?
robinson: Protecting and restoring at the same time is part of the bigger picture. and protect indigenous peoples and cultures from less harm.
This interview has been edited for length and clarity.
