What's at stake if we can't regrow our forests

In 2022, parachutist Luigi Cani dropped 100 million seeds over the Amazon rainforest while skydiving. He did it to raise awareness about deforestation and help regrow the forest. But there has been little scientific follow up to see whether it worked. So, today, we talk to restoration ecologist Pedro Brancalion about the surprising complexity involved in regrowing a forest, and when dropping seeds from the sky – by people or by drones – could work. If you liked this episode, check out our others on building microforests in cities http://lnk.to/PaZ3Mw and scientists’ creative idea to save a keystone tree species http://lnk.to/eatdH8 that grows very slowly. Interested in more tree science? Email us your question at [email protected] mailto:[email protected]. Support public media with NPR+ and enjoy perks for over 25 podcasts like this one. This show’s perks include sponsor-free listening. Learn more at plus.npr.org http://plus.npr.org. See pcm.adswizz.com https://pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences. NPR Privacy Policy https://www.npr.org/about-npr/179878450/privacy-policy

• 0:00Speaker 00

  This message comes from Planet Visionaries. Host Alex Honnold sits down this season with extraordinary doers creating real climate solutions. Listen or watch wherever you get your podcasts.

• 0:12Speaker 01

  Hey, Regina Barber here with a request. Follow us on whichever app you're listening from. We love sharing cool and important science stories with you, and following us means you'll always know when our next episode is ready for you, just like this one.

• 0:26Speaker 00

  You're listening to Short Wave from NPR.

• 0:31Speaker 01

  Around 1930, logging, fire, grazing, and land conversion decimated Hawaiian forests. Because so many trees were lost, rainwater that would otherwise be retained by the land was washed out to sea. And botanist Harold Lyon had an idea to fix it: drop almost 1,700 pounds of tree seeds out of an aircraft 2,000 feet above land.

• 0:57Speaker 01

  This is an early example of aerial seed dropping, where an airplane or helicopter drops a bunch of seeds from the sky in an attempt to reforest the land below.

• 1:08Speaker 02

  Since the last 10,000 years, when humans started to expand agriculture and replace native ecosystems by cultivated ecosystems, we have lost nearly 2 billion hectares of tree cover, which is equivalent to twice the size of the US.

• 1:25Speaker 01

  This is Pedro Brancalionão, a restoration ecologist at the University of Sao Paulo in Brazil. He says Brazil tried a version of this in the 70s to try regrowing forests. Famously, in 2022, parachutist Luigi Cani skydived with a refrigerator-sized crate over a degraded section of the Amazon forest. In midair, he pried it open, releasing 100 million native seeds. But Pedro worries the efforts were wasted, and the seed drop was little more than a stunt.

• 2:01Speaker 02

  So restoration, it's not about just releasing seeds where we want to have trees. Releasing seeds can be part of a solution, but it's just a minor issue considering all of the other more challenging barriers we have to overcome to make restoration happen.

• 2:20Speaker 01

  Restoring a forest is so complex that generally, seed bombing reminds him of a quote from journalist H.L. Mencken.

• 2:28Speaker 02

  I don't remember it exactly, but it's something like, for every complex problem, there may always be a simple, elegant, and wrong answer.

• 2:45Speaker 01

  Today on the show, how to really regrow a forest, and what's at stake if we can't figure it out. I'm Regina Barber, and you're listening to Short Wave, the science podcast from NPR.

• 2:59Speaker 03

  Stay tuned for the following announcements and messages from our sponsors. This message comes from NetSuite. AI isn't just opening new business opportunities, it's changing the way businesses get work done. That's the idea behind NetSuite Next, the next generation of NetSuite, with AI woven into the tools your business already relies on. If your revenues are at least in the seven figures, get the free business guide, Aligning for the Agentic Era: How AI is Changing Everyday Work, at netsuite.com/shortwave. This message comes from Edward Jones. Where they believe rich is more than caring about the latest and greatest, it's also about taking care of what gives your life meaning. That's why your dedicated financial advisor meets you where you are, with personalized

• 3:44Speaker 03

  financial strategies that help protect what matters, so you can preserve your progress while creating a path forward. The key to being rich is knowing what counts. Let's find your rich together. Edward Jones. Member SIPC. This message comes from the Sierra Club. Fighting to protect America's national parks and forests. These public lands are the nation's legacy, and their future is worth fighting for. Donate at sierraclub.org/npr.

• 4:14Speaker 01

  So when you're trying to reforest land, the way you go about it depends on the kind of land you're working with. Like, if an area is completely deforested and stripped of trees versus it being burned in a huge wildfire, the way you go about reforesting the area is different, right?

• 4:32Speaker 02

  Yes, it's different. So it's different because the first and most important issue is which is your goal with this reforestation initiative? And who are the stakeholders in charge of making this decision? Because if you're talking about reforestation in a reserve, in a protected area that burned, okay, you have the government, and probably you may want to bring the native trees back. But if you're dealing with a farmer that relies on that land for getting income for a living, then probably you would have to think about

• 5:17Speaker 02

  an alternative way of reforestation that allows income generation and to profit from this land use. And then you have second and more technical-oriented steps, like which species, which methods. And then if you decide to plant the trees, if you're going to do it with seedlings, with machinery, tractors, or drones. So there is a sequence, a decision-making sequence. And this sequence is hierarchical.

• 5:48Speaker 01

  What are the other things you might have to consider before you drop those seeds?

• 5:54Speaker 02

  Yeah, so first, we need to define what kind of forest we want to have. And then you need to select your plant materials, like the species you want to plant. Secondly, you need to create favorable conditions for these plant materials, whether seeds or seedlings, to establish and grow. So for instance, if you plant the tree seedlings today, and there is no rain, they may die in a week. Because they have been grown in

• 6:35Speaker 02

  a forest nursery with two, three irrigations a day. At the same time, usually, we do reforestation in kind of degraded lands, where we have, at least in the tropics, a lot of leaf-cutter ants. So if you just plant your tree seedlings, your delicious tree seedlings for the ants, before controlling the ants, in one night, you may lose all of your seedlings. At the same time, you may lose your seedlings through competition with invasive grasses. So if you don't control them, they may just kill the plants you want to establish.

• 7:10Speaker 01

  So what you're saying is that you really should take care of the land before you start planting. So you need to get rid of those grasses, you need to take care of that ant problem before you start reseeding?

• 7:21Speaker 02

  Yeah, that's the challenge. It's a before, during, and after. Because the invasive plants, they will recognize the site, the ants or the deers, they will always be around. In addition to it, you may have to prepare the soil for receive the seeds or the seedlings. Because quite often, we are working with areas where the soil has been compacted or with limited nurturing availability. So it's a type of agriculture, let's say. So for me, forest restoration is like promoting the health of an ecosystem.

• 8:03Speaker 02

  So I see myself as a kind of physician of the forest.

• 8:08Speaker 01

  Where you can't just see the patient once.

• 8:10Speaker 02

  Yeah, exactly. So it's the same as dropping seeds in a degraded site. You have a much more complex and difficult-to-resolve problem that doesn't rely only on a single intervention, but on a holistic perspective on the problem and how to address it.

• 8:33Speaker 01

  So lately, some companies have focused on this idea of aerial seed dropping, using something called drone seed bombing. This is where a drone shoots a protected seed into the ground. So what are some of the challenges with using drones to seed bomb land?

• 8:47Speaker 02

  I think the main challenge is regarding the preparation of land for receiving the seeds. So imagine a seed, like as a baby. You must protect it from the beginning. You cannot just release it in a site. Yeah, maybe it's not a good analogy with a baby, but it means that it must be protected.

• 9:12Speaker 01

  Yeah.

• 9:13Speaker 02

  So if you just shoot a seed in an area full of invasive plants with degraded soil and compacted soil and herbivores that may eat the small seedlings, you know, what are the chances of these seeds to germinate, establish, and the trees to develop? Very low.

• 9:38Speaker 02

  So I think the main challenge is not to see seed bombing as a solution, but as part of a technological package.

• 9:48Speaker 01

  Let's talk about the consequences for all of us, for all humans, if we don't reforest places like the Amazon.

• 9:56Speaker 02

  Right, so you may imagine that at the local scale, if you don't have the trees covering these slopes, you may have a lot of erosion during heavy rains. And this soil may be deposited in the rivers and lakes and water reservoirs and reduce not only the quality, but also the availability of water to local people. It may reduce the generation of energy in reservoirs with high-power facilities. It may create problems for the use of the area for tourism. But you may also consider transboundary effects of the lack of trees.

• 10:39Speaker 02

  So for instance, in the Amazon, the trees, they evaporate, transpirate a lot. They absorb a lot of the water from the soil and just release this water in the atmosphere. So that are estimations that an important share of the rain coming in central Brazil results from the south of the Amazon. And if you consider local people, if you have local indigenous people, they rely on these forests for surviving.

• 11:12Speaker 01

  Yeah, and speaking of that, what are the reforestation efforts like right now? How are they doing?

• 11:18Speaker 02

  Yeah, so we are exactly at the mid of the United Nations' decade on ecosystem restoration, so in which many reforestation efforts have been promoted. We have the BOM challenge, which is a global ambitious forest landscape restoration initiative that aims to reestablish 350 million hectares of forest landscapes globally. So there has been many governmental, multilateral initiatives, and especially private initiatives in the past years because of the market of carbon credits.

• 11:58Speaker 01

  Yeah.

• 11:59Speaker 02

  I am part of a company that is restoring tropical forests in Brazil for selling carbon credits in the market and using this source of revenue to expand reforestation in the country. So this is one example how things are working now, are heading to.

• 12:18Speaker 01

  Are you optimistic that these efforts that have started, like you said, pretty recently, that they will increase or that they're doing anything?

• 12:26Speaker 02

  I'm optimistic because so far, I work with Tropical Forest Restoration for 20 years now. And so far, most of my projects, they were established because people were some way obliged to do it. I participated also in projects in which NGOs and well-intentioned people, they just wanted to bring the tropical forests back because of biodiversity, local livelihoods, and so on. But the capacity to scale up based on these two main sources of support, let's say, legal compliance and good intentions, in most of the cases, without money, are limiting.

• 13:06Speaker 02

  But when reforestation for, you know, delivering environmental outcomes become a business, then you have much more resources, support in finding ways to make this process more effective, scalable, and cheaper. And it's exactly in this context that drone seeding makes sense.

• 13:31Speaker 01

  Wow.

• 13:31Speaker 02

  The forests, they are the pharmacy, they are the grocery store, they are the temples. The forest, they are everything for them. So there are, you know, multiple problems at varied scales, in a nutshell.

• 13:49Speaker 02

  I truly believe it's a central issue for humanity, and I hope we can together find solutions to make it happen, but real solutions, not just fake solutions or sexy solutions that are great for advertising, but not for changing this difficult reality we all live together.

• 14:10Speaker 01

  Yeah, not simple, elegant, wrong solutions.

• 14:13Speaker 02

  Exactly.

• 14:15Speaker 01

  Pedro, thank you so much for talking with us about reforestation.

• 14:19Speaker 02

  You are welcome.

• 14:24Speaker 01

  If you liked this episode, check out our other tree-focused episodes on the effort to build microforests in cities and scientist-creative solution to save a keystone tree species that grows very slowly. This episode was produced by Burley McCoy and edited by showrunner Rebecca Ramirez. Tyler Jones checked the facts. Jimmy Keeley was the audio engineer. I'm Regina Barber. Thanks for listening to Short Wave, the science podcast from NPR.

• 15:03Speaker 00

  Stay tuned for the following announcements and messages from our sponsors.

• 15:07Speaker 03

  This message comes from Angie. When it comes to home projects, it matters who you hire. Angie has been helping homeowners find skilled pros to get their home projects done well for over 30 years. Angie's nationwide network has experts in everything, from landscaping to roofing and more. Read verified reviews, see photos of past work, and request and compare quotes to find your best price, all in one place. Download the free Angie app today or visit angie.com. That's A-N-G-I dot com.

• 15:40Speaker 00

  This message comes from the Breast Cancer Research Foundation. This Breast Cancer Awareness Month, the Breast Cancer Research Foundation is doing more than raising awareness. They're funding answers. Your support funds top breast cancer researchers, developing groundbreaking new treatment options, improving screening tools, and getting closer to a world where no one hears the words "you have breast cancer" at all. Today's research is tomorrow's cures. Donate at bcrf.org/support.