Monarch butterflies: They are the iconic symbols of international cooperation in North America in the face of climate change. Because of their long distance migration across a variety of climates and habitats, monarchs serve as a messenger of the collective global effects of climate change interacting with a variety of other stressors, natural and human-triggered. Their numbers on the North American continent are less than 10% of what they were two decades ago, so there are international efforts initiated in collaborative conservation to ensure their recovery. But for the meantime, here is what they are telling us about climate change:
1. The disappearing oyamel fir forests in Mexico are expected to decline beyond their capacity to support monarchs’ winter roosts as global warming affects germination, seedling establishment and survival, tree longevity and wildfire frequency. Losing these high altitude forests in central Mexico could affect the water supply in and near Mexico City since much of their water comes from these watersheds. In addition to the loss of the natural wonders of the forest is a cultural one as well. The people of Mexico have revered the monarchs for centuries for their key role in the Dias de los Muertos ceremonies: the Mexican Day of the Dead.
2. As the oyamel forests become more fragmented, monarchs themselves are increasingly vulnerable to catastrophic freezes that can kill many millions of monarchs on a single night. Farmers in the central highlands of Michoacan also face additional challenges making a living with these dramatic climate changes. They need water and therefore need intact forests to protect/provide the local water.
3. Monarch winter roosts on the Pacific coast of Baja and Alta California are already affected by prevailing drought and warmer winters, with the most southerly roosts being progressively abandoned. Replenishing native trees, shrubs and perennials along the California coast would benefit monarchs and other pollinators by restoring the rich diversity of native plants as larval host plants and availability of nectar-rich flowers.
4. Monarch nutrition during migration will likely be affected by the “phenological mismatches” between incrementally earlier flowering of milkweeds and other nectar-rich flowers, and the northward arrivals of monarchs themselves. This will also affect migratory hummingbirds and neotropical songbirds that depend on the fruits, nuts, seeds and berries available only from effective pollination.
5. Monarch egg-laying may be affected by the scarcity of milkweeds, which have been decimated by both herbicides and drought to the point that 1 to 1.5 billion milkweed stems have been lost from summer breeding grounds in the last fifteen years. Fewer milkweeds in Texas would negatively affect the spring’s first-generation monarchs in years with heavy fire ant predation on monarch larvae and also from extreme weather events.
6. Monarch larval survival may also be at risk by the scarcity of milkweed larval host plants in the summer breeding and feeding grounds. This creates a remarkable opportunity for schools nationwide to participate in active Citizen Science programs by planting, caring for, and monitoring native Asclepias milkweed species in their local school yards, back yards, church yards and court yards.
7. Milkweeds are perennial native wildflowers that not only provide monarchs with critical foliage required for their larval cycle and native bees with needed nectar, but also sequesters carbon in the soil that counters greenhouse emission buildup.
8. Taking agriculture out of row annual forage crop production and planting perennial prairies and savannas with milkweeds in them also retains carbon and pollinators while providing climate-reliant native forages for livestock and bison.
9. Engaging federal, state and county agencies in planting perennial milkweeds and wildflowers along roadsides, railroad lines and energy transmission lines further builds carbon-sequestering corridors across our landscapes useful for monarchs and other migratory wildlife.
10. Reducing the use of fossil fuel based agrichemicals and transitioning to a more sustainable agriculture is not only good for wildlife like monarchs, but adds resilience to our food system.
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