| The Magazine of the CALIFORNIA ACADEMY OF SCIENCES |
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HABITATS Monarchs Hail The Eucalyptus
One monarch butterfly weighs less than a gram, but the collective weight of thousands has transformed this community. No one knows just when monarchs started coming to the little eucalyptus grove on the edge of Ellwood Mesa, just a few miles north of Santa Barbara. They probably have flown here for centuries in small numbers and rested where they could in the vegetated creek valleys, seeking out other havens when the area’s frequent fires raced through before them. No native lore, fossil, or other evidence suggests that anything like the massive over-wintering swarms that gather here today occurred before the Australian eucalyptus trees were planted as windrows in the 1800s. Now it looks like Ellwood’s monarchs, and their human advocates, have saved the eucalyptus grove from the bulldozer. In the process, they have preserved the rare vernal pools and many threatened and endemic plants and animals that call the 137-acre mesa home. The charismatic butterflies supercharged the local environmental community, drawing out, or creating, activists from preschoolers to retirees. The insects are at the center of local schools’ science curriculums and they bring in visitors from around the world. “Save the Monarchs” stickers adorn mailboxes, bumpers, and signposts throughout the city of Goleta and for miles around it. The butterflies are even responsible for the founding of Goleta itself; the city was incorporated in 2001 largely to grant local residents more influence over the area’s environmental destiny and, specifically, the protection of the butterflies’ overwintering site on Ellwood Mesa. Cynthia Brock, the city’s mayor, stepped naturally into her new role from that of butterfly activist. For more than three decades a succession of private landowners has tried to develop Ellwood Mesa, first into a shopping center and then into various types of housing complexes. One early plan proposed building 300 homes that would have obliterated Ellwood Main, the primary butterfly site, paved over the mesa’s 26 vernal pools, and laid waste to the mesa’s ecology. At least ten other proposals have been submitted since then. Each has been rejected or stalled to death. It’s easy to see why developers are drawn to the mesa. In an area where coastal bluffs are frequently hard to access, Ellwood is broad and almost flat, rising to about 70 feet above sea level. The views from the bluffs are spectacular. As oceanfront property becomes harder to find in fast-growing and affluent Santa Barbara County, land like this has become red hot. But Ellwood Mesa is also invaluable to an unusual collection of plants and animals. This is a major biogeographic transition zone. Several southern species find their northern limits here. Several northern ones find their southern limits. The overlapping northern and southern species form unique associations and a flurry of strange hybrids. Much of the mesa itself is underlain by impermeable clay, causing pools to form in the rainy season. Known as vernal pools, they sometimes sprout successive bath-ring-like circles of flowers and other plants as they shrink through the dry spring and summer. Ninety-five percent of the historic vernal pools in the Santa Barbara area have been built over, and Ellwood’s 26 pools represent the largest undeveloped contiguous set of vernal pool and grassland habitat in southern California. Among the vernal pool plants are coyote thistle, wooly heads, popcorn flower, and spike rushes. “These are unique assemblages and no vernal pools like these exist anywhere else in the United Sates,” says University of California Santa Barbara Natural Areas Manager David Hubbard. About two hundred species of birds also use Ellwood Mesa, including white-tailed kites, burrowing owls, northern harriers, and common meadowlarks. The beach below the mesa serves as critical nesting habitat for the western snowy plover, a federally listed threatened species. The plover chicks, in the words of long-time Ellwood activist Christine Lange, “run around looking like marshmallows off-centered on black toothpick legs. They scoot and stop way ahead of their papas—a hopeless chaperone job!” Though exotic grasses have overwhelmed parts of Ellwood, there is a regionally rare 40-acre swath of native grassland with such southern California species as purple needle grass, California barley, and blue-eyed grass. Ironically, the plant that has been most important to Ellwood’s salvation is not a native at all. Monarchs find the groves of Australian eucalyptus ideal as overwintering sites, surpassing local natives such as sycamores and oaks. Eucalyptus are evergreen, they create excellent windbreaks, and their leaf and branch structures are ideal for monarch clustering. Each elongate leaf allows plenty of room for several butterflies to hold on and the leaves are close enough to allow adjacent groups of butterflies to touch one another. Clustering helps the butterflies to conserve their precious warmth through the coolest winter nights. Monarchs east of the Rocky Mountains migrate to the highlands of Mexico to spend the winter. Those to the west make their way to the Pacific coast, settling in sites from Mendocino County to Baja California. The insects are more rugged than they look; they can fly 100 miles a day and take a licking from wind and rain. But they are extremely choosy when picking their winter digs. A grove of trees must have a broad southern exposure; it must be large enough with a sufficiently dense understory to create an insulated interior space; there must be local sources of food (nectar, preferably from milkweed) and water; and a narrow temperature range: cool but not freezing days punctuated by warmer ones. The eucalyptus grove at Ellwood Mesa, which is tall and dark and bisected by lovely Devereux Creek, meets all of those requirements. The butterflies love it. Clustering monarchs can be easy to miss at first. They cling to the eucalyptus leaves, forming bunches of hundreds of individuals that hang like huge bunches of grapes. They huddle close together to conserve body heat. When the sun comes along in the morning, shafts of light cut through the trees like spotlights. They illuminate and warm clusters of butterflies, which explode into orange and black clouds of activity as the insects disperse in a search for water or food. By January of this year, more than 20,000 butterflies had gathered in the Ellwood Main. Some years, as many as 100,000 come. The monarchs begin to arrive in October and by November have gone into a semi-hibernative, energy-saving mode called diapause. Mating begins in January and by March they are headed east on their spring migration. The monarchs that overwinter at Ellwood lay their eggs in the foothills of the Sierra and die. The next generation flies over the mountains to Nevada and spreads out across the West. One or two more generations are born and die before the chill of fall forces the descendants of the previous year’s migration west and south again. Ellwood may be the largest monarch overwintering site in California and is certainly among the most accessible to human visitors. The number of people who migrate here to see the monarchs may match that of the butterflies. Tour buses, school groups, and lone travelers come throughout the season. And some of the two-legged migrants outdo the butterflies in distance traveled. During my few hours at Ellwood I met amateur lepidopterists from Tennessee, Chicago, and Dresden. Two years ago, the land conservation group Trust for Public Land stepped into the decades-long battle over Ellwood’s future by brokering a land swap between the owners of the mesa and the city of Goleta. The deal would pay the developer $20.4 million, plus 38 acres of nearby city-owned parkland (on which the developer proposes building 70 homes) in exchange for the mesa, which would become the property of the city of Goleta. The Trust for Public Land has already raised $13.4 million. The plan is undergoing public review and both representatives from Goleta and the developers think it will fly. With a few modifications, so does Christine Lange, a 15-year veteran of the Ellwood battles. Lange is the president of Friends of the Ellwood Mesa, the local conservation organization that has spearheaded the effort to save the monarchs and their surrounding habitat. If the plan works, there will be plenty of credit to spread among the heroes involved: the dozens of grassroots environmentalists like Lange who refused to give up on Ellwood until a workable solution was found; the Trust for Public Land, for recognizing a great deal when it saw one; and the developer, Bob Comstock, for being willing to think, and build, outside the box. Perhaps the most unlikely heroes of this story are the Australian eucalyptus trees, alien invaders who are on every Native Plant Society hit list, but who are paradoxically the protectors of the monarchs all along the Pacific Coast. Of course, it is the persistent, stunning, durable, and foul-tasting butterflies themselves who are clearly the most royal of the heroes on Ellwood Mesa. And somehow they manage to make it look like they’ve been doing it forever. Gordy Slack is a freelance science writer and a contributing editor for California Wild. |
