(12-14) 04:00 PST Ashland, Ore. — In the natural world, animals take cues about when to migrate and when to mate from the hours of daylight, the temperature and the amount of rain and snow. Here in the Applegate Valley, for example, every spring the yellow-and-black anise swallowtail emerges from its cocoon just as the wildflowers it feeds on bloom.
That’s the way it’s supposed to work: a natural synchronicity between seasons and species, born of evolution and adaptation. But now nature’s timing is off.
After three decades of warming not seen in more than 1,000 years, spring arrives earlier around the world. As species shift their ranges toward the cooler poles or higher elevations, the season brings unexpected arrivals of migrating birds and mistimed hatchings of insects and flowerings of trees.
Some species on the move may flourish, but others may die. And the loss of just one kind of plant or animal, scientists say, can set off a cascade of biological events that can extinguish a whole ecosystem.
Everything’s connected: A tiny plant feeds a butterfly that pollinates a tree that shelters birds that eat pests that attack whole forests.
Disruptions in life cycles are widespread already. Some birds arriving in England from Africa miss the peak food supply of insects or plants. Marmots hauling out of hibernation in the Rocky Mountains early find their food still covered with snow.
It starts with a trickle, and it can end with extinction.
In the heart of the anise swallowtail territory near the California-Oregon border, researcher Jessica Hellmann and a couple of graduate students chased butterflies this past spring. Jumping over bushes and dodging wildflowers, Hellmann snapped her nylon net over a velvety swallowtail perched on a lomatium, a wild relative of parsley.
Hellmann, 32, an assistant professor at the University of Notre Dame , was trying to learn what the swallowtail and another butterfly, the Propertius duskywing, can tell us about the effects of climate change on species. The goal is to find what characteristics — such as body size, breadth of diet and ability to relocate — indicate a species’ chances for survival.
“Which ones do we need to worry about?” she asked.
Hellman was one of the first scientists to link global warming to the disappearance of a butterfly population — the bay checkerspot on Jasper Ridge in Palo Alto.
Paul Ehrlich, the eminent conservation biologist at Stanford University, had studied the bay checkerspot since the 1960s. In 2001, Hellmann and other doctoral students working with him found that climate change played a role in the butterfly’s die-off.
As temperatures climbed and the frequency and severity of extremely wet and dry years increased, the Bay Area’s annual browning of terrain occurred earlier in many years, killing off plantains, the favorite plant food of the bay checkerspot caterpillar, just at the time it needed the food. The bay checkerspot couldn’t find food by moving because neighboring habitat had been covered by houses and highways.
The butterfly disappeared from Jasper Ridge. Now scientists are producing more and more studies investigating the subtleties of climate shifts and what the changes mean for the future of other species, from mollusks to mammals.
In April, Hellmann set up experiments in Ashland, the heart of the swallowtail and duskywing territory, and on Vancouver Island in British Columbia, the northern edge of the territory, so she could compare how the butterflies fared under different conditions.
“The edge of the range is where the action’s going to be” as species travel to find compatible temperatures, she said. "If a species is going to move its range, some individuals have to colonize toward the poles.’’
Hellmann is testing the hypothesis that under a changed climate, a butterfly like the swallowtail will do better at the northern edge of its range than the duskywing. That is because the swallowtail is a generalist: Individuals in one area appear to have the genetic traits of other swallowtails across their entire range, she believes.
The duskywing, in contrast, appears to be a specialist, having only the genetic traits of other duskywings within its immediate population.
If the climate continues to warm, such specialists as the duskywing may not be able to adapt. They then would reproduce less and have fewer numbers to move north in response to the shifting conditions, according to the hypothesis. The species could decline in numbers and become at greater risk of extinction.
In contrast, generalists such as the swallowtail would do better under a new, warmer climate at the northern edge of their range, reproducing more readily and having more numbers to help push the range north.
Hellmann and her students conducted most of the fieldwork from May to July, in full flight season. On sunny days in Ashland, the butterflies alighted on aster, camas, wild onion and iris flowers and delicately fed by dipping their proboscis into the nectar. Hellmann caught a female in her net and took it back to a lab set up in a rented house. There she would hold it until it laid eggs on oak leaves and parsley.
Then she would take the eggs back out to the field and place them in net cages around the species’ favorite food plants. As caterpillars emerged, she would measure the rate of their growth and compare it to caterpillars on Vancouver Island.
Back in her lab at Notre Dame , scientists would examine the DNA that makes up the butterflies’ genomes. The DNA shows how similar individuals are and how closely they are genetically related.
Scientists can’t know what is happening to whole ecosystems unless they look up close, as species miss cues for migration and reproduction, Hellmann said.
“It’s hard to sit in your armchair and dream up what those indirect interactions might be. I would argue that those kinds of surprises are going to be important for a lot of species’ responses to climate change.’’
Tree swallows’ eggs
Just as butterfly researchers in the Applegate Valley in Oregon are trying to learn what traits will enable species to survive climate change, researchers in Lee Vining Canyon, east of Yosemite National Park in California, are studying how tree swallows have altered their reproductive life based on an earlier spring.
If butterfly and bird researchers find answers based on their field and molecular research of two of nature’s most visible and well-studied animals, they say, it will be easier for others to predict which species are vulnerable to global warming and what, if anything, can be done about it.
Tree swallows still show up in the high canyon every spring, after migrating from Mexico, just in time to find a meal of flying insects.
But seven years ago, after studying thousands of observations of when eggs first appeared in swallow nests throughout North America, two biologists, David Winkler and Peter Dunn, found that egg-laying had advanced by nine days between 1959 and 1991.
The study, one of the first to examine a species over the whole continent, concluded that the most likely cause of the earlier breeding was the long-term increase in spring temperatures.
The swallow study became all the more significant when, in the same year, other researchers reported that Mexican jays in southeastern Arizona had increased the time of their first clutch by 10 days between 1971 and 1998. Researchers linked the phenomenon to warming weather.
In August, with Mount Dana in the distance, Winkler, a biology professor at Cornell University, gazed at a metallic green swallow glinting in the sunlight as it soared overhead hunting insects. Sometimes, he said, he almost feels like a swallow, trying to snatch answers to the mysteries of wild species out of the air.
Winkler and his colleagues believe that tree swallows and their eight closest relatives, common throughout the Western Hemisphere, hold the key to how climate affects the way animals regulate their bodies to produce offspring.
“Scientists agree that the timing of the migration has changed over the last four decades due to climate change,’’ said Winkler, who runs a monitoring network in 10 countries for the tree swallows and relatives, including the violet-green swallow in Lee Vining Canyon.
“We’re trying to understand how temperature and food supply affect the fine-tuning of the timing of these events,’’ he said.
As Winkler designs new studies, he is closely watching research in Europe, which has centuries of recorded observations of phenology, or timing, including the season’s first nightingale sighting, bud burst and tree flowering.
Careful observation over time has revealed, for example, that the white storks in the Alps-like Tatra Mountains in southern Poland have shifted their nests uphill to cooler elevations.
Two leading Dutch researchers, Marcel Visser and Christiaan Both, have reported in studies that climate change is mixing up signals all over Europe. "Disrupted synchrony,’’ they say, is probably widespread. And birds seem particularly vulnerable.
The population of the pied flycatcher has declined by more than 90 percent over the past two decades in places where its food supply peaks before the chicks are ready to eat it.
The birds come to Europe from the sub-Sahara and lay eggs on a schedule that hasn’t changed dramatically in 30 years. But their fledglings’ food — winter-moth caterpillars that eat oak buds — is hatching more than a week earlier and is disappearing just when the young birds need it.
Climate and biology
Temperature plays a crucial role in animals’ timing in all sorts of ways. Painted turtles produce more females in warmer years. The great tit, a European bird similar to the North American chickadee, puts on more or less fat.
“We assume that the natural communities are pretty well in balance right now,” said Terry Root, a senior fellow at Stanford who was one of the first biologists to see ecological changes on the ground because of warming. “When we start pushing them with global warming, we’re pushing them out of balance.”
When the yellow-bellied marmot of the Colorado Rocky Mountains emerges from hibernation 38 days earlier than two dozen years ago because of warmer spring air temperatures, it is finding nearly two feet more of snow. Even though the air is warmer, there is more moisture, or precipitation, meaning more snow still on the ground. The result, for the marmot, is less mating or smaller litters.
Root has found studies on more than 400 species of animals and plants that have been changing in abundance and where they live, and 80 percent have shifted in accord with climate change predictions.
“First we had to show that plants and animals were affected by climate,” she said. "Then we had to show that they were affected by warming. Now what we need to do is show how the mismatching is affecting their biology.’’
Another climate scientist, Camille Parmesan, an assistant professor at the University of Texas, has found more than 850 papers noting changes in species and ecosystems that could be attributed to climate change. Coral reefs and amphibians have suffered the most negative effects.
Shifts in range are well-documented for the many ice ages and warm periods of the last few million years.
Scientists have found in the fossil record that when Earth warmed after the last glacial period peaked, about 20,000 years ago, animals and plants that could do so moved toward the poles or to higher elevations.
Species became extinct when they couldn’t move sufficiently to keep up with the rate of habitat change, or when suitable habitat wasn’t available in more northern areas, according to the U.S. Global Change Research Program, an interagency governmental body.
Today, as the bay checkerspot found, habitat might not be available because of human development. Scientists like Root are concerned that that is a new roadblock to species that need to move.
Some species in the past “have endured warming,” she said. "But they didn’t have cities, farms and freeways that they had to get across. They can’t move fast enough in the way that they need to move.’’
ANISE SWALLOWTAIL BUTTERFLY
Papilio zelicaon Lucas
Coloration and size: Wide yellow band on the forewing and hindwing. Yellow-orange eyespot near tails has round black center. Wing span is 2 3/4 inches to 3 1/2 inches.
Life history: Males perch on hilltops and patrol for receptive females. Females lay eggs singly on leaves and flowers of many species in the parsley and citrus families. Young caterpillars eat leaves while older ones eat flowers. Chrysalids hibernate. One brood a year, flies from April to July.
Habitat: Bare hills, mountains, gardens, fields, vacant lots and roadsides.
Coloration, size and song: Shiny blue-green on top with clear white underneath. Female and male adults are similar in appearance. Size is 5 to 6 inches with a wingspan of 12 inches to 14 inches. Whistles and twitters.
Life history: Fly hundreds of miles north every spring to nest. Nest in tree holes; adapt to human-provided boxes. After chicks fledge in August, families break up to hunt alone and gather to roost at night. Migrate south in the fall.
Habitat: Meadows, marshes and forests, always near water.
Sources: Butterflies and Moths of North America, The Butterflies of Canada, Cornell University Lab of Ornithology
PROPERTIUS DUSKYWING BUTTERFLY
Coloration and size: Medium brown forewings with distinct dark markings, and lighter brown fringed hindwings. Clear, glassy spots are small in the mate and large in the female. Wing span is 13/8 inches to 1 3/4 inches.
Life history: Males perch on sunny hilltops to find females. Fully grown caterpillars hibernate. One brood a year, flies from March to July. Adults feed on flower nectar.
Habitat: Open oak woodlands, forest openings and meadows and fields near oaks. Butterfly doesn’t occur in deserts or hot central valleys.
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