High up in the Sierra Madre mountains of southwestern Mexico, almost two miles above sea level, the Oyamel Forest has its own microclimate, a magnet for the Monarch butterflies – who need exactly the right temperature for protection from the weather over winter.
Each Winter, the Oyamel fir trees play host to the biggest butterfly party in the world. Even more remarkable is that those party guests fly in from over 3,000 miles away, using air currents and navigating based on their relative position to the sun, to make the long journey.
Having spent the summer feeding and breeding in the northeastern territories of the USA and Canada, each Autumn, Monarch butterflies embark on the epic migration to specific oyamel fir trees in overwintering ground from which they never return. Instead, it is their great-great-great grandchildren who make it back North. Once they arrive in the Forest two months after leaving, millions of these colourful winged beauties cluster together on the branches of the Oyamel fir, tens of thousands per tree, protected from the wind by the blanket effect of the trees canopy and eco-system.
The humidity in the forest ensures the butterflies wings don’t dry out so they may conserve their energy, while the microclimate keeps the temperature from dipping too high or low, the latter of which would force the butterflies to use their fat reserves to keep warm.
After their winter break on these protective fir trees, the swarms of Monarchs fly halfway back home, mating and laying eggs on milkweed en route. Those eggs turn into caterpillars, which turn into butterflies who fly a little further north and repeat the process.
Four or five generations later the ancestors of those original Monarchs who left Canada during that first Autumn return to the place their predecessors once lived. And so, the cycle continues as millions of butterflies fly to the trusty trees of the Oyamel Forest to retreat time and time again.
However, apart from the declining milkweed population and a growing demand for Mexican avocados meaning some native forests are replaced with avocado plantations, despite Mexico having designated 140,000 aces as protected areas, the Oyamel Firs and the butterflies they protect have another challenge to contend with – climate change.
To keep up with rising temperature, researchers are looking into the possibility of ‘assisted migration’ by moving hundreds of these fir tree seedlings 400 metres up a mountain. Relocation has already begun and currently is being studied as the impact of introducing species to different regions could have a knock-on effect.
But saving important pollinators such as these migratory butterflies may well be worth it, given the fall of the monarchy so to speak – over the past two decades the number of monarch butterflies in North America has fallen by more than 80 per cent as a result of habitat destruction and rising temperatures back home and extreme climate events in the Mexican forests. One thing’s for sure, the story of the Oyamel Fir Tree and their migratory friends is currently entering the part of the narrative arc where obstacles must be faced and, hopefully, overcome. To help save the butterflies, we must take care of where they live, the same is true of all life on earth and trees are integral to that story – our stories are interwoven. Urban trees shade and, therefore, cool their local environment, and also have the capacity to regulate water flow, stabilise slopes and reduce pollution. In doing so they provide ‘ecosystem services’ to those living in leafy suburbs and make them more desirable places in which to live. So, they impact our lives and thus our stories. But more than that, trees stories are often deeply interwoven with our own… read on to find out about the story of Luna.