Tiny Defenders of the Trees Helping Humanity

Tiny Defenders of the Trees Helping Humanity

Mackenzie Thompson

by Mackenzie Thompson

Life Saver, AMC

posted on Jan 23, 2014, at 9:51 pm

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SCALE INSECTS ARE SESSILE (IMMOBILE) INSECTS that lives on plants and sucks at them sometimes it is harmless, sometimes it is fatal to the plants. An emerald ash borer is a scale insect that greatly explains the dramatic decrease in the ash tress primarily in Michigan and surrounding states. The ash borers arrived from Asia in 2002 and since then, tens of millions of ash trees have been killed. This got Rob Dunn, a biologist in the Department of Biology at North Carolina State University and a few of his students to wonder… might this affect humans?

Trees provide many health benefits to human beings…obviously. But also, it has been suggested that the presence of trees possibly leads to a local decrease in some pollutants. This may result in a decrease in health conditions that are relevant to pollution, such as heart disease, respiratory problems, and low birth rate babies. Rob Dunn used the ash borers for a study on the health implications from a loss of trees.

“The anticipated effect of the loss of many trees, in this case many ash trees, would be that in areas where the trees died the health of humans should be more negatively affected. More beetles = fewer trees = more human health problems. More beetles might even = more human death,” he writes.

They found out that “the beetle and its effects on trees were statistically associated with more than 21000 extra deaths”! So, in countries where the ash borers killed trees, there were more deaths. There may be other factors, but none happened to show up in the study. Also, they have found that since scale insects prosper more in warm weather, in the warmer cities, it is possible that they kill more trees, which leads to more negative health.

This leads to the question; why don’t all the bugs kill all the plants? How is Earth still green? It’s not because the insects prefer not to eat all the trees, but it is because other animals eat herbivores. For the beetles, the predators that keep things green are parasitoids. These are organisms that lay eggs inside other animals and are one of the most common life forms here on Earth, being more diverse than birds and mammals combined. Many of these parasitoids focus on scale insects. These animals keep things in check by feasting on the beetles that decreases the number of trees which harms our health. So, indirectly, parasitoids may just be saving our lives. Dunn and his team refer to them as “tiny defenders of trees”. The most common one found inside female scale insects is a parasitoid wasp, about 2 mm, of the genus Encryrtus.

Unfortunately, another type of organisms lay eggs inside parasitoids: hyperparasitoids. These kill our little defenders of trees, making them trees’ (and humanity’s) enemy. So, the decrease in the ash trees (due to ash borers) appears to negatively affect our health. The parasitoids kill the beetles but the hyperparasitoids kill the parasitoids that keep the trees. Basically the only thing we humans can do to help tip the scale to our favor is plant more trees. The benefits will outweigh the disadvantages, providing us with fresh air to breath, shade, fruit, beauty and even a swing to swing on!

To read the full article, go to Scientific American

About Mackenzie

Mackenzie is a lover of world travel, photography, design, style and Chinese cooking. She is passionate about working towards a purpose, recently graduated from Indiana University with a degree in Media and Marketing, and is currently residing in Manhattan.

Contact Mackenzie at mackenzie.thompson@advmedcert.com
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