El Paso, Texas - Demand for avocados in the United States has quadrupled in the last 20 years. America's growing love for the fruit may be harming the fragile habitat of the monarch butterfly, whose winter home is in the forests of central Mexico. Those forests are not far from Mexico's avocado orchards, where the majority of the avocados Americans consume are grown.

While high demand has created economic opportunity for farmers, it has also put a strain on the region's natural resources.

Reynaldo Garduño was just 8 years old when he would climb the mountain near his village in central Mexican state of Michoacan and chop down trees. Then he'd take his burro loaded with wood to sell in town. "They'd buy that wood and make toothpicks, Popsicle sticks, ceiling beams and furniture," he said. "We made our living off the forest. It was our means of survival."

A simple corn harvest was not enough to pay the bills. But 50 years later, things have changed. Garduño lives in the village of Carpinteros about 2.5 hours northwest of Mexico City. Carpinteros is an ejido, a self-governed agricultural community where land is communally held. Today farmers there have a new source of income.

"We are producers of avocados," said fellow farmer Guadalupe Velasquez.

Avocado acreage in the state of Michoacan has roughly doubled in the past decade, according to studies by Mexico's National Autonomous University. The rapid growth is partially due to demand from the US. Last year Mexico supplied America with 70 percent of its avocados.

Avocado production has brought Carpinteros economic stability, and the ejido has unanimously decided to stop cutting trees for profit.

"It's no longer necessary," Garduño said. "Plus we've realized that protecting the forest has its benefits. If we log the forest, the soil will erode and lose its ability to retain water. That hurts our crops in the dry season."

Today, the forest around Carpinteros is healthier. That's helpful to the region's most popular tourist attraction — the monarch butterfly. It migrates from the northern U.S. border by the millions to spend the winter here. The monarch depends on tree cover for warmth and protection.

But not all farmers in Michoacan share the same philosophy as those in Carpinteros. Garduño walked across a verdant avocado field at the edge of his village and pointed to a barren hillside in the distance. "That used to be forest," he said.

He pointed to a neighboring community where fellow farmers cut down trees they then replaced with avocados. And they're not the only ones.

"The land best suitable for avocados has all been planted," said Pedro Mondragon, head of the office for rural development in the nearby city of Zitacuaro. "Most of it used to be cornfields. Now, people are clearing forest in order to make room for more avocados."

Mondragon's office used to give out free avocado plants to interested farmers. It stopped four years ago, so as not to encourage deforestation.

"If people see avocados as a way to get some income...that might be fine," said Pablo Jaramillo, an agricultural engineer and researcher at Mexico's National Autonomous University. "But if they expand their orchards by cutting down the forest, that might not be a good idea."

A university study found in the last 40 years approximately 35 percent of forest land has been replaced with avocado orchards. That comes out to 111,000 acres across the state—nearly the same size as the protected forest where the monarch butterflies live. In the last 20 years, the monarch population has dropped by 90 percent. Deforestation is partially to blame.

Jaramillo said that ought to concern humans.

"The way I see the monarch butterfly is as an indicator of how we are protecting nature," he said. "If the monarch disappears, that means that we are not doing something right."

If the butterfly is showing signs of distress, he said, humans may not be far behind.