Monarch butterflies return to California after record low

Drought, destruction and climate change have kept the insects away

The number of orange-and-black Western monarch butterflies wintering along California’s central coast is bouncing back after the population, whose presence is often a good indicator of ecosystem health, reached a record low last year.

Experts pin their decline on climate change, habitat destruction and lack of food due to drought.

An annual winter count last year by the Xerces Society recorded fewer than 2,000 butterflies, a massive decline from the tens of thousands tallied in recent years and the millions that clustered in trees from Northern California’s Mendocino County to Baja California, Mexico, in the 1980s.

Now, their roosting sites are concentrated mostly on California’s central coast.

This year’s official count started on Saturday and will last three weeks but already an unofficial count by researchers and volunteers shows there are more than 50,000 monarchs at overwintering sites, said Sarina Jepsen, director of endangered species at the Xerces Society for Invertebrate Conservation.

“This is certainly not a recovery, but we’re really optimistic and just really glad that there are monarchs here and that gives us a bit of time to work towards recovery of the Western monarch migration,” Ms Jepsen said.

Western monarch butterflies head south from the Pacific North-West to California each winter, returning to the same places and even the same trees along about 100 sites, where they cluster to keep warm.

The monarchs generally arrive in California at the beginning of November and spread across the country once warmer weather arrives in March.

One of the best-known wintering places is the Monarch Grove Sanctuary, a city-owned site in the coastal city of Pacific Grove, where no monarch butterflies showed up last year.

The city, 112 kilometres south of San Francisco, has worked for years to help the declining population of monarchs. Known as “Butterfly Town, USA”, the city celebrates the orange-and-black butterfly with a parade every October.

Messing with a monarch is a crime that carries a $1,000 fine.

Scientists estimate the monarch population in the eastern US has fallen about 80 per cent since the mid-1990s, but the drop-off in the western US has been even steeper.

The Western monarch butterfly population has declined by more than 99 per cent from the millions that overwintered in California in the 1980s because of the destruction of their milkweed habitat along their migratory route as housing expands into their territory and the use of pesticides and herbicides increases.

Along with farming, climate change is one of the main drivers of the monarch’s threatened extinction, disrupting an annual 4,828-kilometre migration synched to springtime and the blossoming of wildflowers.

Monarch butterflies lack state and federal legal protection to keep their habitat from being destroyed or degraded. Last year, they were denied federal protection but the insects are now among the candidates for listing under the federal Endangered Species Act.

Updated: November 18th 2021, 3:32 PM