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Why Wild Places Matter: Because they Keep Us Healthy

Andrew Wetzler

Posted July 16, 2012

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So why do wild places with abundant and diverse wildlife matter?  Well, one reason is that they literally keep us from getting sick.  No, I don't mean that wild places offer us recreational opportunities and a healthier lifestyle (although they do) or that they keep our spirits healthy (although they do that, too).  They actually keep devastating diseases at bay.

On Sunday, the New York Times published a must-read article on the emerging science about the relationship between habitat disturbance, the decline in biological diversity, and the spread of disease.  Here's the key insight:

...a developing model of infectious disease that shows that most epidemics — AIDS, Ebola, West Nile, SARS, Lyme disease and hundreds more that have occurred over the last several decades — don’t just happen. They are a result of things people do to nature.

How?  Two quick examples. First, take deforestation.  As it turns out, one side effect of cutting down intact native forests is that you create ideal mosquito habitat.  And, in many countries, mosquitoes carry malaria, a disease responsible for killing an estimated 700,000 people a year. Thus:

 In the Amazon, for example, one study showed an increase in deforestation by some 4 percent increased the incidence of malaria by nearly 50 percent, because mosquitoes, which transmit the disease, thrive in the right mix of sunlight and water in recently deforested areas.

Second, take the disappearance of foxes.  Scientists have discovered that the prevalence of lyme disease in New York State is closely linked to the decline of foxes.  Foxes prey of mice, who are crucial to the spread of lyme-disease carrying ticks. As a recent article in Scientific American put it:

The foxes were pushed out by coyotes, which have been on the rise since New York lost its wolves. Which were driven away by humans. Who now get bit by ticks.

So think twice if you are ever tempted to dismiss concerns about wild places and wildlife as just so much tree hugger idealism. The wild places we inherited--the last ones that we have left--may quite literally be keeping you and your family safe.

red fox

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Blair knightJul 16 2012 12:02 PM

Foxes are beautiful. It is so important to protect them!

Jane HallauerJul 16 2012 12:22 PM

This is something I never knew. That is very interesting. I have been in love with nature and wildlife my whole life. I love constantly learning is so important for people to try harder to understand about wildlands and wildlife,etc....we need to help our earth.I have been a friend of NRDC for many years. You guys rock!

Lynnie Zsidov-SteinerJul 16 2012 01:05 PM

Do you know how many people I would love to beat over the head with this article? It's always my soap box topic: "Biodiversity/Predators " . Always a hot topic in NE Wisconsin and the UP of Michigan. Thank you!!

Alexander DavisJul 16 2012 01:37 PM

The Lyme epidemic was caused by the deer epidemic. Adult ticks carried by deer produce 90-95% of the tick eggs which develop into the ticks which infect us. In 1930 there were 300,000 deer in the US. Today there are 30 million. Ticks from one deer produce at least 450,000 eggs in one season. Pro-deer activists like to blame the Lyme-infected mice but adult egg-laying ticks will not feed on a mouse. Without ticks to infect us, we are not at risk for Lyme disease. Speaking on NPR "On Point" 7/3/12, Dr. Maria Diuk-Wasser pointed out flaws in the fox report. There were no actual field data, and it was never shown that the mouse population actually changed with declining foxes. Speaking on the same program, nurse practitioner Vicky Buhr linked the explosion of Lyme cases in Eau Claire WI to the huge deer population. The wise residents of Monhegan Island ME ended their Lyme epidemic by removing the deer.

Andrew WetzlerJul 16 2012 02:05 PM

Thanks Alexander, good comment.

I would encourage folks to read the underlying study, any commentary on its limitations, and decide for themselves. You can find a link to the study here:

I do know that the authors did look at deer population growth in Wisconsin as a possible controlling factor and rejected it, in part because the deer population in many areas that have experienced a growth in Lyme disease was actually stable over that period. See figure 57 here:

Finally, I know of at least one other study that has suggested that vaccinating mouse populations may be effective reducing the transmission of Lyme disease:

Brianna QuickJul 16 2012 02:35 PM

I understand the idea that the explosion in the deer population is a key factor in the spread of Lyme Disease. Having said that, there is a reason for the rise in the deer population and that is the reduction in the keystone predator species that keep the deer population in check. The same thing has happened time and time again, such as with Sea Otters and Gray Wolves being hunted to the point of extinction. Once their population decreased, the entire ecosystem of which they were once a part of completely changed leading to either a financial blow or disease increase for the humans that shared those areas, not to mention the havoc it wreaked on the animal and plant populations. Ironically, the hunting and decrease in the population of the gray wolf correlates directly with the statistics mentioned above. In 1914, the US army began killing wolves and continued through 1933. In 1926, it is thought that Yellowstone had eliminated its Gray Wolf population, which lead to the increase and take over of the Elk population. Seems like the deer may have followed in suit. Food for thought when people begin to scapegoat an entire species for a specific problem. It is generally more complicated than anyone likes to acknowledge.

Sally WelterJul 16 2012 04:33 PM

We need Foxes in our eco-system. We have them in our woods, and they are beautiful.

Alexander DavisJul 17 2012 04:57 PM

Certainly the deer population has increased because of lack of predators, including us. Neighborhoods have little woodsy areas perfect for deer, and often no hunting is permitted. Studies which claim that the deer population doesn't matter tend to compare one overpopulated area with another. Yet, Cornell wildlife expert Paul Curtis says the deer density must be down to 6-8 deer per square mile for it to effectively reduce the tick population. The Vineyard Gazette July 13 quotes Tufts Professor Sam Telford stating that the large deer population on Martha's Vineyard is responsible for the large numbers of ticks which infect people. He has counted 300 ticks on a single deer, and one tick can lay 2000 eggs. These develop into the immature ticks which bite mice and us. A practice of two MDs on the Vineyard say they see 50-70 cases of Lyme a week. 63% of tourists don't know there is a tick-disease threat there.

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