Peter Cowan - POST
By ,
Director of Conservation Science

You might want to sit down for this. The monarch butterfly population crash is dizzying. Recent citizen scientist data indicates a 99.4% decline in the western monarch population just since the 1980s. Picture this: for every 160 monarch butterflies in the 1980s, now there is only one.

Mary Ellen Hannibal’s recent guest post, illustrates the causes of this crisis. For those of you who are ready to take action, however, read on. This post is for people like you who are ready to help fight for this species and stand up at this critical time.

Now is the time to act and here’s what you can do to help save this iconic species:

monarch native garden - POST

1. Grow nectar plants (for hungry adult monarchs)

During their annual migration, some monarchs fly over 2,000 miles and as high as 10,000 ft. It is one of the longest known insect migrations on the planet. To make these long flights, monarchs need fuel. And monarch fuel comes from the sweet nectar of flowers.

Grow nectar species in your yard that are native to California to offer something to eat for these flight weary migrants. Native plants will not only help feed adult monarchs, they will also be more adaptable to our changing climate and will attract other butterflies, insects and birds as well.

Monarch - POST

2. Grow native milkweed (for hungry caterpillars)

Milkweed is the only food source for larval monarch butterflies; the caterpillars just won’t eat anything else. This is an herbaceous, perennial, flowering plant that’s easy to grow in a home garden. There are a few considerations you need to make before you get started:

Only grow native milkweed

We strongly recommend only planting milkweed that is native to California. Avoid tropical milkweed varieties that are available at many nurseries as they create a host of problems. The Xerces Society has regional milkweed guides to help you determine which species are native to your area. We recommend narrow-leaved milkweed (Asclepias fascicularis), which historically was the most widespread variety. It’s also available in most plant nurseries.

Do not grow milkweed if you live near the coast 

Milkweed should be planted only where it once occurred naturally and, north of Santa Barbara, it has never grown close to the coast. To grow it there could distract monarchs on their annual migrations. We only recommend planting milkweed more than 5 miles inland. So, for those of you who live in San Francisco County, San Mateo County and parts of Santa Cruz County, please do not plant it. You should instead focus on nectar plants (see above). If you’re in Santa Clara County or other parts of the state – grow milkweed!

3. Help steward overwintering sites

There are two populations of monarch butterflies (western and eastern) separated by the Rocky Mountains. In the fall, as temperatures start to drop, the western population migrates to California to seek shelter in the relative warmth of the coast.

It’s here in the Golden State that western monarchs form clusters called “roosts,” typically on large trees out of the wind. In the safety of the roost they enter a state of hibernation and rest until it’s warm enough to begin their reproductive cycles. Roosts, in some parts of the state, can harbor thousands of sleeping butterflies.

Of all the roosts within the state, there are many here in the Bay Area that you can visit. The organizations, volunteers and communities that are working to manage and protect these locations need our support, and visiting them is one way to do that. If you’re really committed, you can also join the leagues of citizen scientists helping to monitor and steward these sites (more on that below).

monarch - POST

 4. Become a citizen scientist

We need more eyes keeping a lookout for monarchs and milkweed. It is through these observations that we have been able to track the decline of this species. The data generated by citizen scientists will also support the potential for listing the monarch as an endangered species. This data will also be how, hopefully, we monitor the recovery of this species.

You can report your sightings using the Western Monarch Milkweed Mapper (WMMM). Sightings during the period when monarchs leave their overwintering sites (Feb-Apr) are especially important, a time period that’s not as well documented.

If you live near an overwintering site and can make a longer-term commitment, you should also consider joining the Xerces Society’s Western Monarch Thanksgiving Count. Each year, these groups of dedicated volunteers gather critical information about the population size and health of the habitat.

                                

About Post

Peninsula Open Space Trust (POST) protects open space on the Peninsula and in the South Bay for the benefit of all. Since its founding in 1977, POST has been responsible for saving more than 77,000 acres as permanently protected land in San Mateo, Santa Clara and Santa Cruz counties. Learn more

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