Freshly planted trees at the end of a school oak planting trip.
When you think about tree planting projects, a few common images might come to mind. A smiling face with a freshly transplanted sapling. Gloved hands patting down soil around a growing seedling. Groups of volunteers digging holes together. Planting trees can be a fun, rewarding, almost cliché way individuals can contribute to improving the environment. Trees help filter air, provide fresh drinking water, create habitat for plants and animals, and can help sequester carbon and curb the effect of climate change. In recent years, an enormous number of NGOs, governments, corporations, and nonprofits, and other groups have launched tree planting initiatives, including programs like the World Economic Forum’s One Trillion Trees project (1), the Nature Conservancy’s Plant a Billion Trees campaign (2), the Arbor Day Foundation (3), and Trees for the Future (4). As Fagan et al. write, “National pledges … have brought forest landscape restoration into the center of the global discussion on ways to combat climate change, prevent species extinctions, and improve rural livelihoods” (5). Throughout my time in my GrizzlyCorps fellowship up to now, I have had the opportunity to learn a great deal about these tree planting campaigns and some of the unexpected controversy surrounding them.
I am almost four months into my time with the Napa County Resource Conservation District (Napa RCD). Like all RCDs, Napa RCD is a non-regulatory special district whose stated goal is “to promote responsible watershed management through voluntary community stewardship and technical assistance”(6). My work has primarily focused on supporting the Forest Health program area and assisting in other program areas, particularly the Education and Outreach teams, as needed. One project I’ve been working on with both teams is a deep dive into best practices for monitoring tree plantings.
Napa RCD is part of Re-oaking North Bay, an initiative developed in cooperation with the San Francisco Estuary Institute and the Sonoma Resource Conservation District, funded by the North Bay Watershed Association. The primary goal of this project is to restore lost historic native oak tree communities to the North Bay, which by many estimates has declined more than 90% in the past two centuries. The stated goals of the initiative are to re-establish healthy oak populations, provide habitat for wildlife, provide genetic connectivity within and across valleys, build sustainable populations under climate change and the threat of wildfire, and provide ecosystem services such as cooling, carbon storage, and runoff reduction (7). To support the re-oaking project, Napa RCD works with community members and other organizations to plant native oaks across the county. Right now, this mostly takes the form of community oak planting days. Napa RCD plants trees with volunteers, school groups, and other community members and has been tracking survival rate using a volunteer monitoring team. The team is working towards scaling up plantings, and one of my projects involves exploring different methods for monitoring plantings.
Students on a school planting trip completing an activity about ecosystem benefits and carbon sequestration.
Students completing another activity.
As it turns out, monitoring tree plantings is a surprisingly complicated and somewhat vexing topic. I was initially planning on writing this blog post about how different initiatives like the ones listed in the first paragraph track and monitor their tree planting efforts. As I started writing and doing some research, I discovered several scientific journal and news articles with titles like, “The Surprising Downsides to Planting Trillions of Trees” (8), “Planting Trees Won’t Stop Climate Change” (9), and “Are Huge Tree Planting Project More Hype Than Solution?” (10) and decided to explore further. The idea of planting trees to combat climate change is not a new one, but it is one that has taken off in a whole new way in recent years. The basic science behind it is well understood – trees, through photosynthesis, reassemble the hydrogen, carbon, and oxygen found in water and carbon dioxide into carbohydrates and oxygen, therefore reducing the amount of carbon dioxide in the atmosphere. However, many scientists have pointed out that increasing the number of trees is not necessarily the solution to all of our climate change woes, and as Karen D. Holl from UC Santa Cruz and Pedro H.S. Brancalion from the University of São Paulo point out, “…tree planting becomes problematic when it is promoted as a simple, silver bullet solution and overshadows other actions that have greater potential for addressing the drivers of specific environmental problems, such as bold and rapid steps to reduce deforestation and greenhouse gas emissions” (11).
A common theme among several of these reports is the importance of taking local context into account when planning reforestation and restoration efforts. Alan Buis from NASA’s Jet Propulsion Laboratory summarizes several key questions to consider (12). The first question is how long it will take for reforestation to influence atmospheric carbon concentrations. For a forest to become a carbon sink, the trees must photosynthesize faster than the soil respirates. This means that forests usually take about 10-20 years to become carbon sinks, so realistically, tree planting goals require decades to achieve (13). A related issue is that most tree planting projects set targets of how many trees to plant, rather than how many survive over time, or whether desired benefits are achieved (14). Carbon dioxide can linger in the atmosphere for about 100 years, so when countries or organizations make use of carbon credits for forest preservation, the offset is only effective if the trees remain intact for a century (15). A 2019 ProPublica report found that carbon credits don’t offset the amount of pollution they claim to, or bring about gains that are often quickly reversed or can’t be accurately measured to being with (16). Additionally, carbon sinks can become carbon sources very quickly. Droughts and higher temperatures are constantly stressing forests, making them more prone to mortality due to feedback loops involving wildfires and pests (17).
Even if projects are able to fully meet their goals, it is necessary to monitor whether or not restored areas persist. For example, following the 2004 Indian Ocean tsunami, about $13 million was spent in Sri Lanka on forest restoration, but monitoring found that over 75% of the planting sites had a tree survival rate of <10% due to poor project planning and a lack of maintenance (18). In 2019, a government initiative in Turkey called Breath for the Future planted 11 million trees, but up to 90% of the saplings were dead within three months (19). In Mexico, a 2018 government program paid farmers to plant trees, but in many cases, mature trees were cleared to make room for the new plantings (20).
Another key question proposed by Buis is whether grassland and savanna ecosystems can sustain increased tree over (21). Trees planted in the wrong place can do more harm than good. Ansel Adams, famed California landscape photographer, once wrote, “I cannot think of a more tasteless undertaking than to plant trees in a naturally treeless area, and to impose an interpretation of natural beauty on a great landscape…”(22) Many ecosystems, like prairies, naturally don’t have trees and have been degraded by tree planting projects (23). Ecosystems like grasslands and wetlands can use less water and sequester carbon faster and more effectively at higher temperatures. They can also be more resilient to destruction by fire, drought, and disease. Coastal wetlands, including marshes, mangroves, and seagrasses, can also store carbon more effectively as sea level rises (24). Some of these ecosystems can hold a lot of carbon under the surface – however, subsurface carbon storage can be difficult to quantify (25). It is also important to consider how converting non-forest lands to forests might compete with other land uses (26). Fagan et al. write that restoration commitments can be difficult to meet without the complete transformation of food production systems (27). Land conversion can come at a cost to farming, food production, logging, or other land uses (28).
An additional question Buis raises is how global reforestation would affect Earth’s surface albedo and evapotranspiration (29). Trees, especially evergreen conifers, are less reflective than bare ground, snow, and grasses, and so they absorb more energy from the sun, which is ultimately emitted as heat. At high latitudes and elevations, this can mean that increased forest canopy can lead to warmer net temperatures rather than the desired cooling effect (30).
Another big issue in large-scale reforestation efforts is the use of monoculture. Many large initiatives don’t divulge what species they plant, and few commit to planting native species. Many plant non-native monoculture species. These trees, like eucalyptus, grow quickly in a wide range of climates but are often harvested frequently for timber and can cause problems with erosion, water availability, wildlife habitat, and natural hazards (31). These issues with eucalyptus species are likely familiar to many Californians. Non-native species can overtake local populations and can even displace agriculture from the land being reforested to other areas already occupied by native forests, leading to further deforestation (32). The carbon offset industry will often allow businesses to plant any trees, anywhere, which means that non-native monoculture plantings may be used.
My main takeaway from these reports is that yes, of course it is important and helpful to plant trees, but more trees are not necessarily always the answer. Sometimes restoration means taking trees away. As anyone familiar with climate issues in California knows, years of fire suppression and poor stewardship of forested land has resulted in overstocked forests that are extremely susceptible to things like wildfires and beetle infestations, especially in drought conditions. In Napa County, a significant portion of which has been burned by wildfires since 2017, one of the main issues facing forest landowners right now is how to make their forests more fire-resilient, which often involves significant thinning of trees. One primary role Napa RCD’s Forest Health program currently plays is assisting landowners with technical and financial assistance to get this work done.
When planting trees, it is important to do so in the right place at the right time, and to consider the local ecological context. As Coleman et al. write, ”if policymakers wish to promote forest restoration through tree planting, then the underlying social and ecological processes that led to forest degradation and loss in the first place need to be addressed”(33). It is equally as important to acknowledge and empower local rural and indigenous populations who manage and depend on these ecosystems for their livelihoods. Reforestation efforts should focus most on protecting existing forests, planning for new plantings long-term, and working with communities at the local level to ensure trees and forests can play the role they need to in climate change adaptation and mitigation. I am happy to be working on a project with Napa RCD that I believe strives to accomplish these goals, and I’m looking forward to learning more about how these things can be achieved as the year goes on.
Mike Jones from UCCE showing the patterns bark beetles make when they feed on a tree’s cambium
Up close of the above, with a bark beetle shown as well.
Jason Wells from Sonoma RCD talking to the group during a site visit in Lake County
Pomeroy, Robin. "One Trillion Trees - World Economic Forum Launches Plan to Help Nature and the Climate." World Economic Forum, 22 Jan. 2020, www.weforum.org/agenda/2020/01/one-trillion-trees-world-economic-forum-launches-plan-to-help-nature-and-the-climate/.
"Plant a Billion Trees." The Nature Conservancy, www.nature.org/en-us/get-involved/how-to-help/plant-a-billion/#:~:text=The%20Nature%20Conservancy's%20Plant%20a,us%20plant%20more%20trees%20today.
"Let's Plant 500 Million New Trees." Arbor Day Foundation, www.arborday.org/a-tree-can-be/?utm_source=google&utm_medium=paid-search&utm_campaign=08616-brand&utm_term=arbor%20day&utm_content=brand&gclid=CjwKCAiA76-dBhByEiwAA0_s9SEJ9HB1WzHfCs3e8b61kcHkVMmfHd-2_BqTf2KJeFWR-0tYO12y0BoCXdsQAvD_BwE.
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Holl and Brancalion, 2020
Holl and Brancalion, 2020.
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Holl and Brancalion, 2020.
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Holl and Brancalion, 2020
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