Earth Day: A Dream on Elm Street

Earth Day: A Dream on Elm Street

By Erika Sayuri Naruzawa

Every year, Earth Day campaigns are introduced to increase awareness on the need of a sustainable environment for our planet and to stress climate changing issues. April 22 marks this “green” loving day. The Earth Day theme for 2016 is “Trees for the Earth”. The goal for the 50th anniversary of Earth day in 2020 is to plant 7.8 billion trees, that is one tree for every one of us!

Why Plant a Tree

There are many reasons to plant a tree on Earth Day. Trees absorbs excess CO2 from our atmosphere, helping to combat global warming. Trees also absorb pollutant gases such as nitrogen oxides, ammonia, sulfur dioxide and ozone out of the air and help communities and their economy in a sustainable way by providing revenue, food and energy. Another reason to plant a tree on Earth Day is more on the aesthetic level to restore tree landscaping in cities and make the world more “green”.

What’s Killing Our Trees

Many diseases and pests have been attacking trees in the US such as the Dutch elm disease (DED), the Asian long-horned beetle, the emerald ash borer, and sudden oak death. DED is a good example of tree disease since it practically exterminated elms in Europe over a century ago. In North America, this disease decimated hundreds of thousands of elms after the 30s and it is still an overwhelming threat. The very susceptible American elm, the favorite tree in the urban USA areas due to its shade and cathedral-like canopies, is the victim of this disease. The beauty of tree lined promenades of American elms is currently missing in many US cities.

Combating the Infamous Dutch Elm Disease

Elm breeding programs focus on DED resistance. It is worth pointing out that research on resistant trees must be connected to the research of the pathogen causing the disease. In the Netherlands, in the 60s, the elm hybrids ‘Commelin’ and ‘Groeneveld’ were released with resistance to Ophiostoma ulmi, the less aggressive species of the pathogen that causes DED. The lack of knowledge that a new, more virulent species, Ophiostoma novo-ulmi, existed and in which both hybrids were susceptible to, caused a shake in the elm breeding program in that country. Poor knowledge on the pathogen and its virulence could jeopardize years of plant breeding research, as seen in this example. The good news is that research has been conducted to reintroduce the American elm. ‘Valley Forge’ and ‘New Harmony’ are the only American elm cultivars resistant to this disease available to the public. Furthermore, these two resistant cultivars and resistant hybrids of European and Asian elms have currently been evaluated in 15 states to its resistance to DED in the National Elm trial.

Thanks to studies in plant pathology and fungal biology there is hope on restoring those gorgeous elm-arched lined alleys that once embellished American streets. Whether during Earth day or not, let’s combat global warming and restore beautiful landscapes on our streets by planting trees! Use the hashtag #trees4earth to join the conversation on social media!


Mittempergher, L., & Santini, A. (2004). The history of elm breeding. Forest Systems, 13(1), 161-177.

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