# Three threats to the monarch butterfly’s winter habitat and what we can do about it

*Published:* 2016-12-20
*Author:* Audrey Archer

![Monarchs cluster on oyamel fir branches to stay warm. Tens of thousands of monarchs can cluster on a single tree. ](https://blogs.edf.org/growingreturns/wp-content/blogs.dir/52/files/2016/12/4386426758_001dd5e50e_n-300x200.jpg)Monarchs cluster on oyamel fir branches to stay warm. Tens of thousands of monarchs can cluster on a single tree. Photo credit: [Pablo Leautaud](http://www.flickr.com/photos/98478281@N00/4386426758) [(license)](https://creativecommons.org/licenses/by-nc/2.0/)Just as some people travel great distances to spend the holiday season with family and friends, monarch butterflies, too, make a long journey to spend the winter gathered together in the oyamel fir forests of Mexico.

The eastern population passes through Oklahoma and Texas on its annual migration south, stopping periodically to fuel up on nectar, ultimately reaching their destination in the mountains of central Mexico.

Unfortunately, the monarch’s winter home is under stress, which has contributed to a 90-percent decline in the species’ population over the last two decades.

**Climate change**

The monarch butterfly’s overwintering habitat is made up of oyamel fir forests which thrive only at high altitudes on mountains where the climate tends to be cooler. If the temperatures are too high, monarchs expend their fat reserves more quickly and are less likely to make it to their [Texas breeding grounds](https://blogs.edf.org/growingreturns/2016/06/06/monarch-butterflies-get-help-from-texas-ranch/) at the onset of spring. But temperatures that are too cold are just as devastating to monarchs.

![During the night, it can be up to 10⁰F warmer under the crown of the oyamel fir forest.](https://blogs.edf.org/growingreturns/wp-content/blogs.dir/52/files/2016/12/graph-300x187.png)During the night, it can be up to 10⁰F warmer under the crown of the oyamel fir forest. Source: [Brower et al. 2011](http://academics.hamilton.edu/biology/ewilliam/publications/BrowerEA2011JLepSoc_reduced.pdf)The dense canopy of the oyamel fir forests maintains the microhabitat necessary for monarchs by acting as a blanket, keeping them warm enough at night by retaining heat from the ground, and acting also as an umbrella, which protects them from rain, wind, and snow.

Climate change has the potential for diminishing this blanket and umbrella, because as temperatures rise and water supplies diminish, the forests will become stressed and more susceptible to disease and pests. As trees die off, they could create a hole in the protective canopy. This is already taking place in the lower range of some forests.

Over time the climatic conditions will have changed so much that suitable habitat for the firs will shrink and shift upward along the mountain range. It would take many generations before the trees could migrate to these regions – far longer than is necessary to keep up with climate change.

\[Tweet “3 threats to the monarch butterfly’s winter habitat, and what we can do about it, via @GrowingReturns @audarcher https://edf.org/hC7”\]

**Extreme weather**

![Models suggest that by 2090, there will be no suitable habitats for the oyamel firs within the Monarch Butterfly Biosphere Reserve – the only place where the forests are protected by the Mexican government. ](https://blogs.edf.org/growingreturns/wp-content/blogs.dir/52/files/2016/12/crown-dieback-300x225.png)Trees suffering from crown dieback are not suitable habitat for monarchs. Models suggest that by 2090, there will be no suitable habitats for the oyamel firs within the Monarch Butterfly Biosphere Reserve – the only place where the forests are protected by the Mexican government. Source: Saenz-Romero et al. 2012The population of monarch butterflies has historically had drastic dips and spikes. That’s because the monarch is a sensitive species greatly impacted by [extreme weather events](https://www.edf.org/blog/2016/05/26/how-climate-change-affects-monarch-butterfly-and-what-we-can-do-about-it).

In January 2002, the species experienced unprecedented and catastrophic mortality due to a rare freeze at its overwintering site in Mexico, killing an estimated 500 million butterflies. That’s more than two times the size of today’s population.

Even more recently, between 2015 and 2016, excessive winds and storms knocked down trees, which resulted in the degradation of nearly 180 acres of forest in the Monarch Butterfly Biosphere Reserve.

The frequency and duration of these extreme weather events is expected to increase with climate change, posing great threats to the dwindling population.

**Forest degradation**

The monarch’s overwintering habitat is also threatened by logging and the conversion of habitat for agricultural use.

![This is an example of how all three threats are interrelated, which I think is a good point to make when listing off threats. They are not isolated but have the ability to magnify impacts.](https://blogs.edf.org/growingreturns/wp-content/blogs.dir/52/files/2016/12/108217188-300x199.jpg)Debris flows that result in landslides can be initiated in deforested zones, but more research is needed to establish the possible relationships between deforestation and landsliding.In February 2010, a severe landslide killed 19 people and caused major damage in Michoacán – home of the Monarch Butterfly Biosphere Reserve. This landslide event is believed to be a result of deforestation.

Bordering the monarch’s oyamel fir forests are farming towns that are clearing land to make room for avocado orchards, cutting oak and pine trees that form a vital buffer around the mountain forests where the monarchs roost.

**What can we do to protect the overwintering habitat?**

Aside from mitigating human contributions to climate change, we can help monarchs adapt by protecting and restoring habitat, building resistance to key threats like invasive species and pests, and facilitating the migration of habitat to areas that will be suitable in the future.

My colleagues and I are currently working with partners from academia, government, and agriculture to increase the resilience of monarch populations in the United States, with targeted efforts to restore habitat in the [Corn Belt](https://blogs.edf.org/growingreturns/2016/08/25/what-would-it-take-for-a-nebraska-corn-farmer-to-grow-milkweed-for-monarch-butterflies/) and in key areas of [Texas](https://blogs.edf.org/growingreturns/2016/06/06/monarch-butterflies-get-help-from-texas-ranch/) and [California](https://blogs.edf.org/growingreturns/2016/07/18/why-two-california-farms-give-me-hope-for-the-monarch-butterfly/) – the latter being a state that provides significant overwintering habitat for the monarch’s western population.

[Bringing solutions to scale](https://www.edf.org/ecosystems/monarch-butterfly-habitat-exchange) – across the U.S., Mexico and even into Canada – will be crucial to changing the monarch’s trajectory and making sure they have a safe and warm place to roost for many winters to come.