Dear Tree : Whenever I walk past you, your beautiful leaves bring a smile to my face. Whenever I stop in front of you and take a deep breath of fresh air, I appreciate the oxygen that you produce. Without you and all your friends, we humans wouldn't be able to get enough oxygen. By the way, I noticed that a family of birds has made a nest in your branches. It's so kind of you to provide them with a home. I hope that more people realize how important you and all the other trees are to the environment. Have a nice day! Believe it or not, trees in Melbourne, Australia receive emails like this all the time. How is it possible that trees have email addresses? And why are people sending them messages?

Australia's millennium drought. This drought lasted from the late 1990s to 2010. By the time it ended, 40 percent of the city's 77,000 trees were in a state of declining health. Furthermore, the overall number of trees was decreasing. As a result, the amount of shade provided by trees within the city, also known as canopy cover, decreased. The loss of canopy cover is a major threat to urban environments because it raises temperatures. Higher temperatures in cities can be dangerous for residents, as they increase the risk of heat exhaustion. They also lead to a rise in the use of air-conditioning. This speeds up climate change by increasing energy consumption and greenhouse gas emissions.

Something had to be done to deal with the loss of Melbourne's trees. In 2012, the city government announced its Urban Forest Strategy plan. It set the ambitious goal of planting more than 3,000 trees every year for the next twenty years. The plan also involved the creation of an online map called the Urban Forest Visual. This interactive map shows the location of every single tree in the city's parks and along its roads. It uses colors and symbols to indicate each tree's age and genus. Also, users can click on a tree to find out its species and even send it an email. At first, the "Email this tree" function had a specific purpose. It was designed to allow people to easily inform council workers about trees that were damaged or in poor health.

After the map was posted online, something unexpected happened. The trees started receiving thousands of emails, but many of them were not reports about damage or poor health. Instead, they were love letters, poems, greetings, and messages expressing appreciation for the trees. One person wrote, "I love the way the light shines on your leaves and how your branches hang so low. It is almost like you are trying to hug me." The tree mail phenomenon quickly spread, and people all over the world started sending messages. A message that was sent all the way from Russia said, "When I read about this wonderful project, I was inspired to write to you, even though I live thousands of miles away. Although we are separated by a great distance, we share the same planet and the same environment. Perhaps one day we will meet. Until then, I hope you can stay healthy and strong."

The global popularity of the tree mail phenomenon reminds us that we are all connected to nature, and we are all involved in building a more sustainable world. Without collective action from people across the globe, we would have little hope of saving our planet for future generations. Locally, the tree mail phenomenon has inspired many Melbourne residents to offer their own ideas about building an environmentally friendly urban environment. Some have even volunteered to measure trees and monitor animals for nature programs in the city. Meanwhile, the Urban Forest Strategy's tree planting project has remained on track, and canopy cover is predicted to increase from 23 percent in 2012 to 40 percent by the year 2040. Melbourne's urban forest strategy will help keep the city cool. It will also allow residents to interact with nature and engage in outdoor activities every day. As a result, residents will be happier and healthier as they move toward a greener future.