For many years, scientists could only guess at the number of trees on earth. But in 2015, Thomas Crowther and colleagues at the Yale School of Forestry and Environmental Studies used a combination of satellite imagery, forest inventories, and supercomputer technologies to produce a global map of tree density at the square-kilometer pixel scale.

The study published in Nature on September 2, 2015, concluded that 3.04 trillion trees are growing on earth.

Studies also estimate that the number of trees worldwide have declined 46 percent since the onset of agriculture thousands of years ago.

In an effort to increase biodiversity and combat climate change, the United Nations Environmental Program (UNEP) launched a Billion Tree Campaign in 2006. By November 2007, they had achieved the goal, and one billion trees had been planted worldwide.

In December 2011, after more than 12 billion trees had been planted, UNEP formally handed management of the program over to the youth-led not-for-profit Plant-for-the-Planet Foundation (an organization that has been participating in the Billion Tree Campaign since 2007).

More recently, in the World Economic Forum 2020 at Davos, the Forum launched an initiative to bring support to plant a trillion trees by 2030.

If you want to join the tree-planting momentum, the Audubon Society recommends careful research in Plant Trees that Turn Your Yard into a Bird Oasis. Planting a native tree that contributes to life where you live is important, and the Audubon Society is a great resource that will help you select the best tree for your outdoor living space.

If you have a small yard or patio, and you live in California, a great tree for wildlife is the Scrub Oak (Quercus berberidifolia). The Scrub Oak grows 15 feet tall, is evergreen, and supports more than 100 species of butterflies and moths.

A versatile California native shrub for pollinators is the California buckwheat. The California Native Plant Society Orange County (OCCNPS) chapter will be giving away four-inch California buckwheat plants during the April 4 weekend at the Fullerton Arboretum’s Green Scene.

OCCNPS will also be offering a variety of California native plants and trees for sale at  Green Scene. Native plant experts will answer your questions and offer support to help make planting with natives successful and fun. Join us at Green Scene on April 4.