April 22nd is Earth Day! 

This year, the Earth Day Network has identified an important Earth Day theme: Trees for the Earth. This organization is committed to planting 7.8 billion trees by Earth Day 2020; that's one tree per person for every person living on the planet. Why plant trees? They help mitigate climate change, they support communities and economies across the globe, they provide habitat and protect biodiversity, and, everywhere they are planted, they help connect us to our natural landscapes. 
Here in the Greater Yellowstone Ecosystem, we have a lot of trees. We have lodgepole pine trees, aspen trees, Douglas-fir trees, cottonwood trees, whitebark pine trees, and so many more. At Teton Science Schools, we love learning about trees’ interactions with other parts of the ecosystem, and we do our own share of tree planting every spring when we plant willows to improve the riparian habitat along creeks on our conservation property.
Here are some things about trees that I bet you didn't know:
Trees in the Greater Yellowstone Ecosystem
  • 80% of the canopy trees in Yellowstone National Park are lodgepole pines, according to the National Park Service. Lodgepoles are the only pine trees in the GYE with two needles per bundle. 
  • It takes whitebark pine trees as many as 50 years to reach cone-bearing maturity. These trees live in the alpine community, above 8,500 feet, where harsh conditions lead to slow growth.
  • Quaking aspens carry out photosynthesis in their bark instead of just in their leaves, like most trees. Photosynthetic bark allows aspens to continue producing sugar in the winter after they have dropped their leaves. As much as 42% of a young aspen’s chlorophyll is in its bark, turning it a yellowish green.
  • Douglas-fir trees have the greatest range, north to south, of any American conifer, growing from northern British Columbia all the way to central Mexico. Confusingly, Douglas-firs aren’t actually fir trees (Abies) at all; they make up a different genus entirely called Pseudotsuga, or false hemlock.
Trees Everywhere
  • There are so many trees in the northern hemisphere that each summer, when these trees are photosynthesizing, the carbon dioxide concentration in the atmosphere decreases globally. During the winter, the atmospheric carbon dioxide concentration increases again. This is why forests are called “the lungs of the world.”
  • We know that humans are relatively “new” animals, and that dinosaurs are older, with sponges and jellyfish and worms being some of the earliest animals. But what about trees? Conifers are the oldest trees; flowering trees like aspens are younger. One very old tree species, the gingko, originated 200 million years ago and has remained essentially unchanged ever since. It’s like a living fossil, a link to the dinosaurs with which it co-existed. The first gingko predates the creation of the Rocky Mountains by 120 million years; think of all the changes this landscape has gone through since then, while the gingko has remained the same. But the gingko wasn’t among the first trees; those had already been around for 185 million years, creating the earliest forests on earth, forests that towered 30 meters tall and eventually gave rise to much of the world’s fossil fuels.
  • We tend to think of single trees growing from single seeds. But trees can also sprout from buds or nodes at the base, or in the roots of, a parent tree. Root sprouts, also called suckers, can emerge from the ground far from the original plant, sending up a whole new tree that is genetically identical to the original tree, and helping the tree spread itself, its seeds, and its genes across its habitat.
  • Until 2015, no one actually knew how many trees there were on Earth. Then researchers at my alma mater, the Yale School of Forestry, used a combination of satellite imagery and forest inventories to map the planet’s trees. They found that there are more than three trillion trees on earth, about seven and a half times as many as had been estimated previously. 
Join us in celebrating trees this Earth Day!