Of Droughts, Data, and Butterflies

August 21, 2015


Photo: Variable Checkerspot, Euphydryas chalcedona, nectaring along the Castro Crest Ridge, Santa Monica Mountains, May 2015 (Elizabeth Long).

Californians are all painfully aware that we are suffering through year 4 of a significant drought. It's easy to predict that animals that rely on streams, ponds, or lakes are going to suffer from the scarcity of water. Animals that live in water, reproduce in water, or simply need these water sources for drinking are all under an increased risk. But what about things like land-dwelling insects? One of the questions I've been asked often in the past few months is "How are the butterflies responding to the drought?" One might think that would be an easy question to answer, but the reality is more complex.

Butterfly watchers have some common wisdom that they share with each other when it comes to drought: One species isn't affected by a one-year drought, while this other species declines, and yet another species seems to thrive. Maybe a short drought triggers some sort of "now or never" mating response that results in lots of offspring being produced. You can hear the same sorts of generalities being discussed for the second year of a drought. But three years of drought? Four? That's when old butterfly watchers shrug their shoulders and say "this is uncharted territory." And finding data collected in a rigorous enough way to really answer the question of "how do butterflies respond to drought" is challenging. Because, in order to detect a change due to drought, we need to understand what "normal" populations really look like. And unless we can survey one area regularly, methodically, for a long time, we don't have the power to know if the numbers of butterflies we see today represent a decline or are just the status quo or even an increase.

This is where the power of long-term studies can help us understand animals' response to drought. Unfortunately, though, very few research studies are designed with this type of methodology, and most don't carry on long enough to really answer these questions about drought. One of the best long-term studies that I know of is conducted by Dr. Art Shapiro at UC Davis [in the interest of full disclosure, Art was my PhD advisor, and he and I continue to collaborate on research projects]. Art began surveying areas along the I-80 corridor in the 1970s. Today, Art has 10 field sites stretching from the San Francisco Bay Delta up to Donner Lake in the Sierra Nevada Range. He travels to each site every two weeks, walks a regular route, and records the butterflies he sees there. In recent years he and his collaborators have used this dataset to examine how butterflies respond to climate change. Now, Art's data is well-poised to let us ask questions about the response of butterfly populations to drought.

I can't tell you conclusively what Art's data say about butterflies and the drought (he's still figuring that out). But I can tell you what he has noticed in a general sense (and what other observers have confirmed anecdotally): at a given location, the number and composition of butterfly species doesn't seem to have changed much, but the overall abundance of butterflies is way down. And, interestingly, a lot of species seem to be carrying out their life cycles much earlier in the year than normal. This can pose a problem when, for example, abnormal weather events arise, like the monsoonal rain storms that dumped rain and snow on parts of California in mid-summer. Summer snow storms in the Sierras seems to have disrupted several butterfly species' life cycles—they were absent during the annual Yosemite Butterfly Count this July.

Despite the value of these types of long-term studies, it can be difficult to support and carry out such a labor of love. Finances add up, and funding is difficult to obtain when the potential pay-off is some vague day years, decades, or even centuries away. Personnel come and go, while personal lives and health issues can complicate our ability to spend this much time in one place collecting data. Fashions in scientific research can trend away from natural history observational research. But as most scientists will tell you, the more we learn, the more we realize how much there is to know, and nowhere is this as true as for complex ecological systems. How these biological communities respond in the face of extreme environmental conditions can only be answered by careful study, and in this case, many years of hard work.

 


(Posted by: Elizabeth Long)


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Want to know the time of day? Look no further than your wristwatch, clock, computer, or cell phone. For the time of year, though, look to nature. Like a reliable timepiece, certain plants and animals signal the change of season. Just like learning to tell time, anyone can learn to read nature’s seasonal clock. As with so many things here in the Golden State, nature is decidedly different from the rest of the country — our spring really begins in autumn!

The current three-year drought aside, L.A’s Mediterranean climate is usually characterized by cool, wet winters and warm, dry summers. California’s native plants have adapted over thousands of years to this cycle and, even before the first raindrops fall from the sky, some plants begin to emerge from their summer resting phase, sprouting new leaves or bursting into bloom.

Manzanita in bloom

Manzanitas are among these “first responders”. Here in the Nature Gardens, two types of manzanitas started to bloom well before that marvelous, soaking rain around Thanksgiving: the white-flowered ‘John Dourley’ and the pink-flowered ‘Lester Rowntree’. Hummingbirds, butterflies, and bees were spotted visiting these early blossoms to get a dose of sugary nectar, inadvertently pollinating the dainty, fragrant flowers. After pollination, the tiny, apple-like fruits (manzanita means little apple in Spanish) will begin to form and will eventually be eaten by mammals, birds, and even humans. Wherever manzanitas grow, food foragers are rediscovering what many Native American tribes learned centuries ago — manzanita berries and flowers are tasty. You can make cider, jam, and a sugary powder with them.

More than 50 kinds of manzanita (Arctostaphylos species) grow wild in California, typically in sunny areas with fast-draining soils. Intrepid hikers can find them clinging to coastal bluffs or steep mountain slopes or forming impenetrable thickets in chaparral. In the Los Angeles area, head to the Santa Monica and San Gabriel mountains for the best chance of seeing them. Look for their tell-tale smooth, reddish bark and sinuous branches. For adventure seekers of the gardening sort, stroll into a local nursery or botanic garden, where you’ll find a tempting selection of manzanitas, from groundcovers to large upright shrubs.

On your next trip to the Museum, make time to explore the Nature Gardens so you can discover these beautiful manzanitas and other signs of fall, or should I say spring? What a grand way to connect with this uniquely Californian season.

Written by Carol Bornstein


(Posted by: Lila Higgins)


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