Bay Area Science: An Interview with a Kelp Biologist

Meet Sara Gonzalez, a kelp biologist from the University of California, Santa Cruz.

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A view of the Pacific shore from Santa Cruz, Ca. Note the giant kelp floating on the water’s surface in the distance.

Gulls cried in the distance as we walked along the shore at Natural Bridges State Beach. The air was crisp with a twinge of salt. We had passed numerous brown mounds of kelp when Sara excitedly pointed to a kelp mass strewn on the beach closer to the water’s edge. We found just what we were looking for: giant kelp, Sara’s primary study species.

Sara knelt down beside a piece and picked up one of the bladesthe kelp’s leaf-like structures.

“You can see the really deep corrugations here, and the blade’s serrated edge.” She pointed to the corrugations, or grooves, carved into the kelp’s blade. She gently traced her finger along the serrated edges as I watched intently, realizing I would have missed these delicate details had I not been with Sara.

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Giant kelp is widely distributed around the world, found along the coast of North and South America, Africa, Australia, and beyond. Distinct geological regions are home to giant kelp populations that look vastly different – despite being the same species.

“Some of these forms are so distinct that they used to be classified as separate species,” Sara explained. “Now they are termed ‘ecomorphs’ of the same species.” Different kelp ecomorphs, or individuals of the same species with different physical characteristics, vary in the form of their blades and the structures they use to anchor themselves to the ocean floor.

Sara Gonzalez is a graduate student in the Department of Ecology and Evolutionary Biology at the University of California, Santa Cruz. Previously, she studied biology at Cornell University. Trading upstate New York’s bitter winters for warmer weather and sandy beaches, she came to Santa Cruz to study kelp with Dr. Pete Raimondi.

Sara’s work with kelp began during a Fulbright Scholarship project in Chile. There, she collaborated with other marine researchers at the Pontificia Universidad Católica de Chile to study the influence of nutrients from fish excrement on kelp growth. I imagined her on the incredible Chilean coast studying its marine life, acquainting herself with the landscapes praised in poems by the famous Pablo Neruda.

While collaborating with Chilean academics studying kelp, Sara realized how embedded kelp is in today’s society as a natural resource. Kelp is harvested for its alginates, a polysaccharide found within the cell walls of all brown algae. When alginate combines with water, it forms a thick gum-like texture, which can be used in products ranging from cosmetics, daily-use items such as toothpaste, and foods such as ice cream.

“It was an interest that grew over time – being around kelp, and talking to people about kelp all the time. I got really excited about it,” Sara said, smiling and looking out towards the water.

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Sara examining kelp on the beach of Natural Bridges State Beach.

Kelp is a foundation species, meaning it plays an important role in its community. It also forms an entire ecosystem: the kelp forest.

“The high productivity of the kelp forest and varied physical structure from the base to the canopy provide the foundation to support a diverse array of life, including many commercially and recreationally harvested species such as kelp bass, several species of rockfish, and the kelp itself,” Sara explained.

Organisms, ranging from invertebrates to fish to mammals, rely on kelp forests as a place to live, forage, and reproduce. Kelp forests also protect shorelines from erosion by creating drag against waves coming to shore.

Sara’s time in Chile piqued her interest in the morphological differences between Californian and Chilean kelp. This interest grew into a well-formed project as a graduate student. At Santa Cruz, she is studying the environment’s role in determining the kelp ecomorphs and its effects on the production of alginate.

However, today, we were two just two naturalists combing the beach shore.

We approached another mass of kelp, flushing a swarm of small insects as we knelt down beside it. Sara, ignoring the insects, reached down her hands to pick up a kelp mass the size of a soccer ball.

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A kelp holdfast, held by Sara.

“This is the holdfast,” she explained, turning over the ball, which appeared to be a mass of root-looking structures. “It’s composed of haptera, which are these root-looking things.” She pointed out the network of twisting haptera, growing tightly together in a pattern which resembled the creases of a brain.

On our coast, giant kelp forests grow up to 50 meters from the ocean floor, eventually reaching the water’s surface.

“As it grows, the kelp forms more and more of these haptera, until you end up with this big, netted mass of them.” Sara slowly turned over the holdfast for me to see, pointing out the layers the haptera formed. Despite its resemblance to a mass of plant roots, she explained, a kelp’s holdfast doesn’t act like a root system at all. Rather, it’s used by kelp to anchor itself to substrate. She carefully placed the holdfast back near the pile of kelp blades.

Over the course of our walk along the beach, we encountered 3 different species of kelp: the giant kelp with its densely grooved blades, the chain bladder kelp with its line of bubble-like protrusions, and the feather boa kelp, which looked, not surprisingly, like a long feather boa.

However, our giant kelp specimen was by far the most physically impressive. Scientifically, giant kelp is equally astounding: it is one of the fastest-growing plants in the world, accumulating 12 to 18 inches of growth per day. Their high growth rates make kelp forests one of the most biologically productive communities – comparable to tropical rain forests.

Moving forward, Sara plans to continue her kelp studies by conducting a series of experiments. By rearing kelp in the lab and simultaneously planting them in the ocean, Sara will be able to elucidate the importance of environmental versus genetic factors in kelp morphology and alginate production.

Sara’s work in Chile also shed some light on the importance of nitrogen in fish excrement for kelp growth, and its role in reducing blade decay. These preliminary results prompted Sara to focus on the effects of ammonium on kelp – being the nitrogen product from fish excretion, after the ocean’s pH conditions react with the ammonia from the waste. Less is known about ammonium’s effects on kelp when compared to its close chemical relative, nitrate.

“In parts of California, there are times of the year when nitrate levels are reduced, so it is important to understand the potential contribution of fish-derived nitrogen, especially as oceanic conditions in the future are likely to change,” Sara explained.

We continued down the shore, eventually reaching a rockface with shallow pools carved into it. Inside the pools, anemones dotted the edges like flowers, their tentacles spread out like delicate sea petals. Around the pools, masses of washed-up giant kelp spread out like carpets on the rocks.

I thought of the kelp’s holdfast: its dense network of haptera forming a stronghold to the ocean floor as the kelp grows towards the water’s surface. Then, I thought of Sara. Her ideas seemed to grow in an analogous way, forming a dense network of enthusiasm and curiosity to anchor her as she reaches towards the answers.

We returned to the beach and meandered back towards my parked car, absorbed in our conversation as gulls flew overhead.

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Footprints in the sand along Natural Bridges State Beach.

If you are a scientist living in or around the Bay Area and are interested in an interview, feel free to contact bayareanaturalist (at) gmail.com.

Logging, Crumbs, and Lost Fish: The Story of the Marbled Murrelet

Cover photo: © Tom Benson, 2014, some rights reserved.

Did you know that there’s a seabird that builds its nest high up in redwood trees? Learn about the marbled murrelet – from their breeding biology to what we think could be causing their population declines.

Cover photo: © Tom Benson, 2014, Flickr Photo Album, some rights reserved.

Quick Facts

  • Marbled murrelets are seabirds that venture inland to build their nests high up in redwood trees.
  • The health of coast redwood forests affects marbled murrelet populations, since murrelets need redwood forest habitats to breed.
  • Despite considerable conservation of redwood forests, marbled murrelet numbers are still declining by 4 percent annually.
  • Scientists have found that predation by Steller’s jays attracted to campgrounds by human food is affecting marbled murrelet numbers.
  • Since murrelets are seabirds, the health of our oceans could also be impacting marbled murrelet populations.

 

The Mystery of the Marbled Murrelet

Our story begins with a mystery.

Marbled murrelets are robin-sized seabirds that are closely related to puffins and murres. As is the norm for other seabirds, scientists expected the marbled murrelet to nest in large colonies along the rocky coast. Yet no such breeding colonies of marbled murrelets were found, despite the habits of their close relatives. The nesting place of the marbled murrelet remained an unsolved mystery to ornithologists in North America for over a century.

This changed in 1974, when a worker performing maintenance at Big Basin State Park discovered a lone nest high up in a redwood tree. The nest contained a single chick, which strangely had webbed feet. He snapped a photo that was later identified by bird experts as a marbled murrelet youngster. The mystery of the marbled murrelet nesting place was solved.

Defying all expectations of a seabird, these clever nesters fly 20 miles inland to construct nests high up in the cover of redwood trees. With this discovery, the marbled murrelet became the most recent bird species to have its nest found in North America.

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A coast redwood towering over the trail at Big Basin State Park, the site of the first documented marbled murrelet nest. Old-growth coast redwoods are the nesting sites of marbled murrelets.

Logging and the Loss of Murrelets

The California Gold Rush of 1848 brought steep human population increases to the San Francisco Bay Area – and with these population increases also came a huge demand for lumber. Settlers turned to the redwood stands along California’s coast for their supply. The irresponsible logging stripped most of the old-growth redwood forest from our coastline. It is estimated that only 5% of old-growth coast redwood trees survived logging.

Coast redwoods are critical to breeding marbled murrelets. Thus, the declines of redwood forests were closely intertwined to declines in marbled murrelet populations. The low murrelet numbers recorded off our coasts resulted in their listing as threatened under the Endangered Species Act in 1992. In California, they are state-listed as endangered.

The fate of the murrelets, along with other calls for the reduction of logging in the northwest, led to the 1994 Northwest Forest Plan under President Clinton. The plan protected 9.7 million hectares of old-growth forest along the coast of California, Oregon, and Washington.

Despite the protected breeding habitats, scientists monitoring murrelet populations still found that their numbers were declining. The population around California, Oregon, and Washington is continuing to decline by as much as 4 percent per year.

Crumbs, Jays, and Predation

A study at Redwood National and State Parks discovered one potential cause of the murrelet declines: predation by other birds, namely Steller’s jays.

Steller’s jays are crested blue and black birds found along the west coast of North America and south into Mexico. They are corvids, belonging to the same family as crows, ravens, and other jays. In addition to their diets of plant matter and insects, they will eat the eggs and young of other bird species.

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A common sign at campgrounds, featuring a Steller’s jay and a warning to clean up all traces of food. Source: Save the Redwoods League.

Steller’s jays are common at campgrounds, as their varied diet is supplemented by leftover food and crumbs from humans. These “crummy” areas attract jays and increase their density, thereby increasing the chances of Steller’s jays finding and predating the nests of marbled murrelets.

Public education programs are in place to decrease the amount of food left behind by humans. The initiative’s goal is to decrease the number of murrelet predators attracted to a given area. Signs are present in parks, warning people that food waste (even as small as a single crumb) has the potential to impact marbled murrelets.

Ocean Threats Still Loom

Scientists still don’t have all of the answers to what’s causing the murrelet population decline.

One factor affecting their numbers could be the availability of food off our coast. A study in Washington found that 80% of marbled murrelet nest attempts failed due to issues relating to low prey availability.

We do know that more frequent and intense El Niño events caused by climate change are negatively impacting fish populations. El Niño is a naturally-occurring phenomenon in which the number of upwellings of nutrient-rich cold water is reduced relative to “normal” years. Plankton, a main food source for fish, rely on the nutrients from the upwellings. With no plankton to eat, the fish populations (and the seabirds that depend on them) can be negatively impacted.

What does this mean for the marbled murrelet? Our efforts on land can be executed flawlessly, but the dual-lifestyle of this enigmatic seabird makes it so that their populations can still be harmed by threats to our oceans.

Stories such as these bring to light the importance of protecting as many diverse areas as possible. A holistic approach to conservation is necessary to save species that live such diverse lives.

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A view of the Pacific Ocean off the coast of California.

Sources:

Sudden Oak Death’s Grip on California Forests

Oak trees have been in danger in California since the mid-1990’s, and researchers are now predicting a grim future for California’s emblematic tree. The killer, termed “Sudden Oak Death”, has killed an estimated 3 million trees since its introduction to California.

Quick Facts

  • Sudden Oak Death is caused by a fungus-like pathogen. It is fatal to many California-native oak species.
  • Since its introduction to California, the pathogen has killed an estimated 3 million trees.
  • Scientists have concluded that the pathogen’s spread in California is too great to completely eradicate it. Rather, management of the disease in localized areas is suggested to be our best option.

 

A Fatal Pathogen and Its Spread

Something weird began happening to California’s oak trees in the mid-1990’s.

Trees were plagued with a sudden onset of dying leaves and trunks that “bled” dark-colored sap, and locals concerned about the sudden tree deaths reported their observations to specialists.

The pathogen causing the symptoms was identified in 2001 as Phytophthora ramorum, a fungus-like species that infects plants. P. ramorum arrived to California by infested rhodendron plants. The fungus spread across the United States through shipments of nursery plants before it could be detected. It is spread through spores, which can be carried by rain, wind, and infected soil.

The symptoms exhibited by infected plants vary by plant species. Some plants can be infected with the pathogen and not have symptoms serious enough to be fatal, allowing the plants to continue living and spread spores from the pathogen as “carriers”. The California bay laurel is a well-known carrier, since its symptoms are limited to spots on some parts of the leaves and diebacks of twigs.

P. ramorum is known to cause death in a number of oak species, including coast live oak, Shreve oak, and California black oak. P. ramorum is also known to infect a relative of oaks, the tanoak. The main symptom of infected trees is a canker on the trunk, with blackish to reddish sap that “bleeds” from the sore. Infected trees take an estimated 2 years to die from the pathogen itself; however, other pathogens and insects readily infect the already-sick trees and speed up the tree’s death.

A Disease With Far Reaches in California

Since its introduction to California in the mid-1990’s, Sudden Oak Death has killed an estimated 3 million trees along the coast from Big Sur to Oregon. The effects of this disease also go beyond just the deaths of trees – trees that have died from Sudden Oak Death are dangerous fuels for California wildfires, a threat that has become more prominent as we face the effects of climate change.

Management practices have focused on the identification, quarantine, and removal of infected plants as a way to stop its spread. Public education initiatives have also focused on educating California residents on how to avoid spreading the disease, through practices such as sterilizing pruning tools and washing off equipment, tires, and shoes that have come in contact with infected soil.

Predicted spread of the sudden oak death epidemic through California, 1990–2030
An image from Meentemeyer et al. 2011 showing the predicted spread of Sudden Oak Death from 1990 – 2030, based on the assumption of similar weather conditions to those in California from 1990 – 2008.

Despite California’s efforts, a recent study (Meentemeyer et al. 2011) conducted by scientists from Cambridge, the University of California at Davis, and the University of North Carolina has concluded that completely eradicating the disease from California is not possible. The sheer number of trees infected makes it impossible to rid the state of the disease or stop its spread.

Instead, the study suggests that management should focus on the restoration and treatment of small, local forests as the most practical and cost-effective option. One such study focusing on removing dead and diseased trees is currently being conducted around Bolinas Ridge, giving us hope for the development of best management practices moving forward.

Sources

The Bay Area’s Fight for the Western Burrowing Owl

Cover photo: © Nathan Rupert, 2010, some rights reserved.

Learn about the burrowing owl’s current conservation status in the Bay Area and the current initiatives to protect them.

Cover photo: © Nathan Rupert, 2010, Flickr Photo Album, some rights reserved.

Quick Facts

  • The western burrowing owl is a small species of diurnal owl, meaning that it’s active primarily during the day.
  • The burrowing owl used to be common in the Bay Area, but habitat loss has caused a steep decline in their populations over the last 30 years.
  • Local conservation groups are working to improve habitats to make them more attractive to owls, and are working on monitoring sites known to have owls.

 

Nestled on the edge of a corporate development next to the entrance to a local wildlife preserve lies a small, fenced-off lot of short grass. Here, after minutes of scanning small mounds of dirt, Dan and I encountered our first burrowing owls. An adult sat hunkered down, directly next to a young owl that was curiously peering back at me with large, yellow eyes. With this developed backdrop, it is difficult not to question the fate of this charismatic species.

A Bay Area Species in Peril

The western burrowing owl is a diurnal owl, meaning that it’s active during the day. It’s fairly small, standing at about 10 inches high. True to their name, they nest and reside in burrows in the ground – relying on sites that have already been excavated by burrowing mammals such as the California ground squirrel. They can often be found standing vigilant outside of their burrows during the day.

This endearing bird was once a common bird in the South San Francisco Bay Area. In the mid-1980’s their population was estimated to be about 640 individual birds – with three-quarters of the population residing in the South Bay alone. Today, their population has been reduced to isolated breeding and overwintering populations (overwintering populations migrate to the Bay Area during the winter to escape cold temperatures in their other homes). In 2017, the South Bay reported just 64 adults at 5 breeding sites.

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An adult and juvenile western burrowing owl in the South Bay.

Habitat Loss and Evictions

Habitat loss is the main threat that these owls face. The South Bay was once host to native grassland habitats; however, housing and other commercial developments to address a booming human population have outcompeted the owls for space. The East Bay is facing similar problems – areas that overwintering owls need to be successful have rapidly disappeared, putting stress on their populations.

Even at sites where the owls reside, the active removal of burrowing owls takes place. Developers that are initiating projects at known burrowing owl sites will hire contractors to install one-way doors at burrowing owl sites – allowing the owls to leave their burrow, but not to re-enter.

These “evictions” are rendered legal because individuals or nests are not harmed. However, many groups criticize the practice since there is no monitoring of the evicted birds after the traps are installed. Burrowing owls have high nest site fidelitymeaning that they have high rates of returning to the same breeding site, and even specific burrow, year after year. With the evictions taking place without long-term monitoring of the displaced owls, the effects of practices such as these are unknown and the evictors are not held accountable.

Bay Area Organizations Band Together for Owls

Efforts to increase the population of breeding burrowing owls in the South Bay are currently being implemented. A number of South Bay organizations have banded together to increase the population of breeding owls at Warm Springs in Fremont. Based on the outcome of their efforts, they will apply what they’ve learned at this site to the management of other sites in the South Bay. Similarly, the Santa Clara Valley Audubon Society is working in Alviso, a neighborhood in San Jose, to provide suitable habitats for the owls. The group works to install artificial burrows and mow the area to keep vegetation short.

In the East Bay, the Golden Gate Audubon Society, the City of Berkeley Marina and the Shorebird Nature Center have joined forces to create the Golden Gate Audubon Burrowing Owl Docent Program. The program focuses on raising public awareness about keeping dogs on-leash to help protect the overwintering owls that use the areas in the East Bay. Docents also keep track of the burrowing owl numbers in their area – allowing for long-term population data.

Efforts such as these provide hope for burrowing owl populations, yet their fate is still undecided in the face of the rapidly expanding Silicon Valley.

For more information on how to volunteer for the Golden Gate Audubon Society’s Owl Docent Program, please visit this page and scroll to “Train to Become a Docent” towards the bottom of the page. For more information on volunteering with the Santa Clara Valley Audubon Society doing habitat restoration at Alviso, please visit this page.

Resources

The Brown Recluse: How Dangerous Is It?

Cover Photo: © Andrew Hoffman, 2012, some rights reserved

Recluse spiders are some of the most feared spiders in America. Rumors of infestations, highly dangerous bites, and even deaths have spread throughout the country. Yet despite the rampant arachnophobia, brown recluses are actually not so dangerous when we take a closer look at the spider behind the hype.

Cover Photo: © Andrew Hoffman, 2012, Photo Library, some rights reserved.

By Dave Frank, Contributor

Recluse spiders are some of the most feared spiders in America. Rumors of infestations, highly dangerous bites, and even deaths have spread throughout the country. Yet despite the rampant arachnophobia, brown recluses are actually not so dangerous when we take a closer look at the spider behind the hype. Let’s explore some common myths and misconceptions about the brown recluse!

Myth #1: Recluse bites are extremely dangerous!

First, we need to address the rates of spider bites in general. There are many myths about spider bites. One common myth is that you can tell a spider bite from another bug bite, such as a mosquito bite, because a spider bite will have two puncture wounds while a mosquito bite will only have one. While it is true that spiders bite with two fangs, in contrast to the bite of a mosquito’s single mouthpart, spider fangs are usually too small and close together for us to actually see both bite marks. A spider bite would appear as a single wound, much like a mosquito bite. In fact, mosquitos are responsible for far more deaths worldwide than spiders.

According to Rainer Foelix’s Biology of Spiders, “only four genera are known to cause potentially deadly bites.” Loxosceles reclusa, the American brown recluse, is one of these spiders, but most recluse bites are harmless. The venom of spiders is used to paralyze their prey, so bites on humans would only be defensive. And this is a rare case, as recluses (as with most spiders) are not aggressive towards humans. They are actually much more scared of us than we are of them!

Their bites are necrotic, which means that their venom causes tissue degeneration at the site of the bite. This is different from spiders such as the black widow, Latrodectus mactans, which have neurotoxic venom. Neurotoxic venom will cause nerve damage and paralysis to prey. For humans, the bite of a recluse is very unlikely to lead to significant injury or death. We are much larger than their usual prey, so their bites do not contain enough venom to hurt us much. As long as one seeks medical attention for wounds causing pain or that won’t heal, recluse bites are survivable.

Myth #2: Brown recluses are common in California!

In America, the range of the brown recluse is contained mainly in the southern states. While there have been sightings in California, these are extremely rare. In fact, an entomologist at University of California, Riverside argues that there are no populations of brown recluses in California. Rick Vetter states that hundreds of spiders have been brought to the entomology department at UC Riverside for identification, and not a single one was a brown recluse.

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Recluse Range Map, taken from UC Riverside Entomology Department, http://spiders.ucr.edu/recluseid.html

The map above shows the common ranges of recluse spiders in the U.S. Loxosceles reclusa is the species of brown recluse with bites that are the most medically significant. As you can see, their range does not extend west into California. While other recluse species can be found in California, these species do not have bites that are medically significant. Loxosceles deserta, the desert recluse, can be found in California, but they live far from urban areas and so are not considered dangerous due to their extremely limited interaction with humans.

Myth #3: Recluses are aggressive spiders!

As stated previously, recluses are not aggressive. There’s a reason they’re called “recluses” after all! Recluses like finding hidden spaces to build their nests. Older homes can be perfect habitats for them, but they often coexist peacefully with humans. As far as infestations go, there are many reports of recluses being found in large numbers. However, most of these events are blown out of proportion. In Brentwood, TN, a woman claimed to have been bitten several times due to an infestation in her apartment. However, the articles do not always have scientifically accurate information and may be misleading. For example, the main picture of “brown recluses” in this article does not show a brown recluse, as the spider shown is not even brown! While recluses can be found in high numbers in suitable locations, it is extremely rare for them to interact negatively with humans.

Myth #4: Brown recluses are difficult to tell apart from other spiders!

Brown recluses are quite easy to identify. The most telling feature of a recluse is the pattern of the eyes. Most spiders have eight eyes arranged in two rows. Recluses have only six eyes, and these are arranged in three pairs across the cephalothorax (head and torso region). They also have a violin shaped pattern along their backs, which is why they are sometimes called “fiddleback spiders”. Recluses are around ⅜ of an inch in length, a little smaller than a penny, and are have uniform brown coloration. Other spiders may have some of these aspects, but if a spider you are trying to identify does not have these characteristics, then you have not found a brown recluse.

Brown Recluse Spider
© Andrew Hoffman, 2012, Photo Library, some rights reserved

For those who may still be arachnophobic, please take a look at this video! This person is holding a brown recluse and a black widow, the most commonly feared spiders, in one hand. As you can see, neither spiders attack the cameraperson. These spiders are actually rather mild-mannered. We do not recommend trying this at home, but hopefully it shows that humans have very little to fear from our eight-legged friends.

Resources

 

Trouble in Paradise: Migrating Monarch Butterflies Face Declines

Cover photo: © Felix, 2011, some rights reserved.

Learn about the Monarch Butterfly, the threats that contribute to their continuing decline, and ways you can help from your own backyard.

Cover photo: © Felix, 2011, Photo Library (Flickr), some rights reserved.

Quick Facts

  • Monarch butterflies make an annual migration to warmer temperatures, with some populations traveling as far as 3,000 miles.
  • Santa Cruz is one of the monarch overwintering sites in California.
  • Monarchs have faced declines over the past 20 years, and 2018 marked the lowest count in 5 years for the California population.
  • Factors such as loss of flowers, degradation of stopover sites along their migration, and the loss of overwintering habitat in Mexico contribute to their decline.

 

It was late December when Dan and I packed up our camera gear and set out for Santa Cruz to see the monarchs. Ever the worry-wart, I anxiously clasped and unclasped my hands the entire one-hour drive over. “What if we missed them?”, I asked, eyes wide with potential disappointment as we wound down Highway 17. It was our first time hearing about the incredible journey of this butterfly, and I was avid about witnessing it for myself despite it being towards the end of their migration.

Racing the sunset, we arrived in the Lighthouse Field parking lot and made our way down a field path leading to a small stand of eucalypts. Rounding the a corner on the trail, we were met with a small cluster of trees dripping in orange. Tiny flutters gave life to the bright masses, which were unmistakably made of hundreds of butterflies.

The Journey South

Most people, myself included, will react in disbelief upon hearing that a delicate orange butterfly migrates thousands of miles to escape cold temperatures. “But migration is for the birds!” they’ll think, when trying to picture an insect achieving such a feat. Sure enough, monarch butterflies are the only known butterfly species to migrate in two directions (north and south), and they happen to overwinter in Santa Cruz, just outside of the Bay Area.

This incredible journey is made by one specific generation of butterflies, termed the “migratory generation”. Cooling temperatures, shorter days, and the aging of milkweed, the primary source of food for monarch caterpillars, signal to the butterflies that it’s time to begin the journey south to escape cold temperatures.

There are two populations of migrating monarchs: one east of the Rocky Mountains, and one west. The eastern population, with individuals from places as far as southern Canada, make their journey down to Mexico where they congregate in the oyamel fir forests. For this population of butterflies, the migration can be as long as 3,000 miles. The western population makes their way over to California’s coast, overwintering in locations from Santa Cruz all the way down to San Diego.

Migration Map Epic Migration
Created by Paul Mirocha for Monarch Watch

Relying on navigational cues such as the Earth’s magnetic field and the position of the sun, the butterflies make their long flight. Upon reaching their destinations, the monarchs congregate together and form large clusters on the branches of trees. This allows the insects to retain enough warmth to survive the winter.

Trouble in Paradise

The Western Monarch Thanksgiving Count is a citizen-science project (a scientific study based on data collected by the public) that stands as the longest-running and most comprehensive count in for the monarchs overwintering in California. Citizen-scientists, biologists, and other professionals join forces for a 3-week long effort to count butterflies at multiple sites.

Monarch Butterfly Count
Xerces Society Western Monarch Thanksgiving Count. 2018. Western Monarch Thanksgiving Count Data, 1997–2017. Available at: http://www.westernmonarchcount.org (For a full list of contributors, see westernmonarchcount.org/about)

But lately, the numbers have been grim. The western population of monarch butterflies has been facing declines over the past 20 years, and 2018 marked the lowest count in 5 years. According to one source, 1.2 million butterflies were recorded on a survey two decades ago. The graph above shows the decreasing numbers, and in 2018 a survey using almost the same number of locations recorded just 300,000 butterflies.

A Complex Decline

Many sources have suggested that the loss of the monarch caterpillar’s only food source, milkweed, has been the major contributor of the monarch decline. However, a recent study on long-term monarch population trends conducted by a Cornell University academic suggest otherwise.

Anurag Agrawal, from Cornell’s Department of Ecology and Evolutionary Biology, wanted to take a closer look at all of the monarch population data. Pulling together multiple data sets, he worked with the intent to identify where the biggest hits to the population occurred along the monarch’s migratory route.

Surprisingly, he found that populations trends appear to be doing the best at points where they are relying on milkweed, meaning that milkweed’s decline may not be the only cause of the monarch population decline. Instead, the problem is happening at points during their migration and in parts of their overwintering sites in Mexico. The degradation of sites that they use to stopover along their migration, the lack of sites with nectar-rich flowers to fuel their migratory journey, and the loss of their overwintering forests in Mexico appear to be the main contributors to population loss.

That’s not to say that planting native milkweeds to help the butterflies will be a vain effort – as providing additional resources to the butterflies can never hurt. However, these efforts can be greatly amplified by other efforts as well. Planting habitats for monarchs to feed in your own backyard, only buying FSC-certified wood (Forest Stewardship Council certification, certifying that the wood has come from a responsibly-managed forest and supply chain), and volunteering for monarch counts are all other ways that we can help.

Public education, in particular, can also work to help the butterflies – for that allows us to approach the complex problem on a unified front. With more people aware, we can work together to save the monarchs before they vanish from our coast.

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© 2017, Mike Bessler, Photo Library (Flickr), some rights reserved.

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