It all started when Jimmy “MrBeast” Donaldson, famous for his extravagant stunts on Youtube, was challenged to plant 20 million trees to celebrate reaching 20 million subscribers on Youtube. And what a crazy world we live in – he might just pull it off.
On Oct 25th, the Internet buzzed with excitement as Team Trees – a collective of social media influencers spearheaded by Jimmy Donaldson and Mark Rober (another YouTuber and former NASA engineer) – officially launched their campaign. In a matter of days, the initiative managed to raise donations small (as little as $1) and large (from the likes of Elon Musk and Jack Dorsey). At the time of this writing, Team Trees has raised an impressive $12 million – all donated to tree charity The Arbor Day Foundation.
Now, I love trees as much as the next person, and raising awareness and money to tackle climate change is always a good thing in my book. But, now seems as good a time as ever to remind everyone that tree planting projects have many potential pitfalls, and we should not be rushing to plant as many trees as possible, as quickly as possible.
The superhero that doesn’t wear capes
First, a biology class refresh. Vox’s Umair Irfan explains the carbon cycle of trees well:
“All plants use sunlight, water, soil nutrients, and carbon dioxide to generate energy and to grow. These plants then die and decay. This returns some of the carbon back to the sky and leaves some carbon in the ground. Over time, this leads to a net reduction of carbon in the atmosphere.”
Since the beginning of human civilization, the number of trees on Earth has dropped by almost 50%. This is bad news. By cutting down forests for timber production, land, agriculture, and mining, we are not only releasing carbons, but also losing the countless environmental benefits trees provide, such as preventing soil erosion and supporting biodiversity. Meanwhile, we are pumping an enormous amount of heat-trapping greenhouse gases into the atmosphere – chiefly through burning fossil fuels.
Tree planting has emerged a promising tool to combat climate change. One highly publicized recent study in Science touted the “mind-blowing potential” of reforestation, estimating that adding 2.2 billion acres of tree canopy could capture 2/3 of man-made carbon emissions. While the precise estimates and assumptions have come under a healthy dose of scientific critique, there is wide consensus that tree planting is a crucial piece of any plans to mitigate climate change.
News flash: forests are complex ecosystems
But despite the best intentions, humans’ track record on reforestation has been mixed at best. It turns out that forestry is complicated (duh), and restoring ecosystems takes much more than planting perfect grids of whatever tree that happens to be cheap and fast growing.
So much could go wrong: there could be the mistakes of planting invasive species that outcompete native trees, or the chance that trees planted in arid regions will guzzle up precious water resources and be prone to fire.
Case in point, a 2016 Science study demonstrated that reforestation in Europe has actually increased global warming. This is largely because of the management practices to replace broadleaved species with conifers. Conifers such as Scots pine and Norway spruce grow fast and are commercially valuable, but their darker leaves absorb more heat than native species such as oak and birch.
The warming effects aren’t small: the authors estimated that the impact was equal to 6% of global warming attributed to the burning of fossil fuels, and cautioned that Europe isn’t the only region that has deployed similar practices.
Location, location, location
There is reforestation, then there is afforestation – planting forests where there has not been forests before. This can be even more harmful, as savannas, grasslands, wetlands, open-canopy woodlands, and deserts all offer their own unique ecosystem services.
The Yatir Forest in Israel offers helpful lessons. Spanning across 7,400 acres in the Negev desert, Yatir was planted in the 1960s by the Keren Kayemeth LeIsrael-Jewish National Fund (KKL-JNF), with primarily coniferous trees such as Aleppo Pine and Cypress. While the KKL-JNF has boasted a lot of environmental benefits of the Yatir Forest, including carbon sequestration, increased rainwater penetration, and the prevention of floods, ecologists have increasingly pointed out the drawbacks of replacing native landscapes.
According to Fred Pearce’s fascinating piece on Yale Environment 360 (which everyone should read stat), the lush greens rising out of the desert come at a cost. New saplings rarely grow without irrigation in the semi-arid region of Southern Israel, and mortality rate is high in dry years. A drought in 2010 alone killed 50,000 trees, with 80% losses in certain areas. Further, introducing tree canopies in deserts and grasslands have destroyed the habitats of ground-nesting birds and native reptiles.
All that is to say, the where, what, and how matter a ridiculous amount when it comes to tree-planting. While we want all trees everywhere to suck up carbon, support wildlife, provide cooling, purify the air, forestation projects simply are not that black and white.
Curse of the kittentails
In addition to reforestation and afforestation, urban forestry faces a whole set of different challenges. City landscape is a harsh environment, often bearing no resemblance to a tree’s natural growing conditions. Recent research has found that urban trees “live fast and die young” compared to their rural counterparts. American Forests estimated that average life expectancy of a downtown urban street tree is just 13 years. Strapped for cash, municipalities often struggle to properly maintain its urban canopies. All of these challenges make urban forestry uniquely difficult.
Let me offer one more cautionary tale on how without proper expertise and foresight, urban tree planting can go very, very wrong…
In the 1960s and 70s, Beijing underwent a massive tree planting effort to mitigate its infamous spring dust storms. As many trees selected for the program failed to survive, around 120 millions of willows and poplar trees were eventually planted for their ability to thrive in the cold, the droughts, poor soil conditions as well as pests and insects. Adding fast growth, dense crown, and low cost to their list of virtues, these were the perfect trees, right?
Well, except: city planners didn’t consider the catkins – the flower clusters that release masses of airborne seeds in these cotton-like fluff. (Catkin, as the Beijinger cleverly noted, comes from the old Dutch word for kitten “katteken”, for a catkin’s resemblance to a kitten’s tail.)
Having grown up in Beijing, I can tell you that even though I’d pick catkins over sandstorms any day of the week, this stuff will drive the most zen among us nuts. Costly to clean up, the flying catkins exacerbate allergies, worsen traffic, and pose major fire hazards. Yes, you read that right – it turns out that the catkins are extremely flammable. During one single week in May 2013, 105 fires were reported involving catkins.
The city has tried a number of fixes to reverse the catkin curse. Pruning the crown, prohibiting the planting of female poplar and willow trees, injecting chemical inhibitors to prevent the buds from forming (with each injection costing $4.6 and lasting only one year) – none has proven effective (or cost-effective). Ultimately, the city is looking at replacing millions of these trees with new breeds, while hosing the catkins down each spring in the meantime.
There you have it, three cautionary tales that demonstrate tree planting is nothing but simple. Team Trees recognizes this, as stated in their FAQ: “We quickly realized that to plant trees in a sustainable and environmentally friendly way we would need to partner with the professionals,” which is why they are donating all funds to the Arbor Day Foundation. To be clear, the Foundation doesn’t do the planting itself; rather, it partners with agencies such as the US Forest Service, so the Foundation’s track record on its tree survival rates is a bit unclear.
On the other hand, Team Trees and the Foundation have acknowledged the importance of responsible planting: “right trees, right place,” maintaining in addition to planting, etc, so I remain cautiously optimistic. At a time of fraying public trust and lack of political will to tackle the climate crisis, it’s easy to want to celebrate every dollar we can get. But as this Think Progress piece and others have rightfully stated: “reforestation doesn’t fight climate change unless it’s done right.” So thanks Team Trees, now let’s get to work.
- A terrific piece from the National Geographic that reminds us the best strategy to regrow a forest may be for us to prepare the ground, and get out of the (trees’) way.
- This Ensia piece explains lessons learned from Japan’s tree planting efforts.
- Reporting from Ireland demonstrates the costs of replacing native habitats with non-native conifers.
- A history of China’s Grain to Green program, and the trade offs between holding back the desert and straining water resources.