Field trip to Rodeo Beach
On September 28, 2019 the Environmental Forum of Marin (EFM) Masterclass 46 met at Rodeo Beach. Terri Thomas spoke about biodiversity hotspots and how they relate to Marin County. Fewer than 50 biodiversity “hotspots” exist in the world with only one in the United States — the floristic province of California. What makes a hotspot? Hotspots are places with a combination of the richest biodiversity and the most threatened plant species. Terri added that these hotspots have been prioritized by one other factor — their resilience or ability to be restored.
Geology of Rodeo Beach
Geologist John Karachewski led us on a tour of the geology of Rodeo Beach. He described the landscape of the Bay Area at vastly different periods of time. The Bay Area is a crossroads where ancient plants came together reaching their northernmost and southernmost limits. We traveled back in time 200 million years —to a time when molten pillow basalt erupted in the center of the Pacific Ocean. Over time, the rock traveled 2000 miles from the Pacific Plate and was deposited onto the North American Plate as the triangular-shaped sea stack we see today on the south end of Rodeo Beach.
We visited several rock outcroppings on Rodeo Beach and learned how they were formed — black basalt, and maroon-colored chert are the primary rocks of the Marin headlands. The chert was formed in deep ocean water far from the continent. It’s made entirely of organic sediment — plankton shells, along with the fallen ash of volcanoes — forming about a foot of build up every million years. The color of chert depends on the amount of iron and oxygen. High oxygen turns chert red and reduced oxygen makes it green.
We learned about the lost Farallon Plate that once resided in the ocean between the Pacific Plate and the North American Plate. 200 million years ago it collided with and was subducted under the North American plate, melted into magma, and rose to form the granite mountains of Yosemite and the Sierra. A small piece of the lost Farallon Plate remains today off the coast of Cape Mendocino.
It took 100,000 big earthquakes over millions of years to move the Pacific Plate northward. The Farallon Islands — not to be confused with the Farallon Plate, are moving slowly north, about an inch a year. They originated on the North American plate but were scraped off when the Farallon Plate subducted. The islands ended up on the Pacific Plate, transported from the Mojave region to their present location in the Bay Area.
Birds and mammals migrate every year. Even trees make a slow migration in search of better conditions over hundreds of years, and surprisingly the land moves too in the slowest peregrination of all, over geologic time.
Farther north in Point Reyes, Tomales Bay marks the divide between two plates, the Pacific and the North American, with the San Andreas fault running between the two plates under the bay. The rocks on both sides are roughly the same age but they are made of completely different substances. The Pacific Plate side (west) is granite and the North American side (east) is pillow basalt.
Sea level rise and carbon dioxide
300 million years ago, the earth was in an ice age and the continents were one land mass. The natural cycle was 100,000 years of frozen ice age followed by 10,000 years of warmth. We are currently in a period of warmth. 15,000 years ago, what is now the bay was grassy plains, and the ocean was 30 miles farther west — about where the Farallon Islands are located. Sea level was 400 feet below what it is today, well below the continental shelf. Sea level has not changed much in the past 2000 years until the 20th century when it starting rising due to global warming. A three foot rise by 2100 is optimistic. It could be as much as 30 feet in some areas. For the last 8 ice ages, the carbon dioxide level in the atmosphere was 200 parts per million (ppm) and 300 ppm during the warm melt periods. We are now at 410 ppm, a rise that would normally have taken 100,000 years to produce naturally. The last time the earth was at 400 ppm CO2 was 2.5 million years ago during the mid-Pliocene, at the time the white cliffs at Drakes Beach in Point Reyes were formed.
On geologic time
Really wrapping your brain around the earth’s many metamorphoses and the vast amounts of times that have passed since its creation 4.5 billion years ago is difficult. The models that show geologic time as a calendar are helpful to me. The earth is created in January; the first multi-cellular organisms appear in the spring; in December dinosaurs appear and in the last 20 minutes before midnight on December 31, humans (homo sapiens) enter the scene — we are a blip in geologic time. So much life has blossomed and been extinguished as Earth evolved.
I’m struck by the contrast between the fragile, fleeting life on the surface of our planet and the persistent, iron heart of the Earth. The thin crust of land and sea coupled with the narrow band of atmosphere support life that is ever-changing. The Earth will endure but that thin band where life exists is a delicate balance of elements that are easily disturbed.
Marine Mammal Center
Adam Ratner, a marine biologist and the guest experience manager from the Marine Mammal Center spoke about the work of the center and how it’s affected by climate change. The center started in 1975 and today is the largest marine mammal hospital and education facility in the world, covering 600 miles of coastal “rescue range” in California and Hawaii. Their vision is healthy oceans and healthy mammals. The center performs 700-900 rescues a year. They have a staff of about 90 and 1400 volunteers, ages 15 to 97! Adam has worked with local animation students at the California College of the Arts to create engaging educational short videos.
As a fun fact, Adam shared that Hollywood has used the screeching sounds of elephant seals for dragons and orcs in popular movies.
One of the short animated videos produced for the Marine Mammal Center focused on Domoic acid toxicosis also called “red tides” which is a toxin produced by a type of algae. It impairs marine mammals and other mammals. Fish eat the algae and marine mammals eat the fish. It causes lethargy, disorientation and seizures. As the climate heats up, more frequent and larger algal blooms are happening. Most algal blooms last one to three weeks but a “blob” in 2015 lasted for months. As the climate warms, this toxin is a growing concern.
Adam presented several compelling case studies that showed how the Marine Mammal Center is monitoring whales, seals and other marine mammals as indicators of climate change impacts as well as the effects of plastics in the ocean on marine mammals.
Call the Marine Mammal Hotline 24/7 to report a sick or dead marine mammal: 415-289-SEAL (7325)
Golden Gate Raptor Observatory
Allen Fish from the Golden Gate Raptor Observatory (GGRO), formed in 1984, gave us a history of their program which traces its roots to Hawk Mountain in Pennsylvania in the 1930’s. Hawk Mountain changed from being a hawk hunting spot to a wildlife refuge. Hawks at the time were considered pests and the government paid $5 a head for dead hawks. Birding enthusiast, Richard Pough set the wheels in motion to cease the slaughter by showing grisly photos of piles of dead hawks to the New York City Audubon Society in 1933. Rosalie Edge took up the cause and raised $3500 to buy Hawk Mountain in 1934 for $2.50 an acre. Hawk Mountain became an early example of eco-tourism where instead of shooting hawks, visitors paid 10 cents to view soaring hawks on their migration. Richard Pough went on to co-found The Nature Conservancy in 1951.
Rachel Carson and Hawk Mountain
Rachel Carson used the data collected over decades at Hawk Mountain for her studies on the effects of the pesticide DDT on birds. DDT stays in the fat layer of fish and birds and most severely affected those raptors whose diet was primarily based on fish and waterfowl such as Osprey, Peregrine Falcons, and Bald Eagles. Rachel Carson published her landmark environmental book Silent Spring in 1962. DDT was eventually banned and more than thirty years later in 1999, these raptors were finally taken off the endangered species list.
High mortality rate
Two out of three juvenile raptors don’t survive their first year (50-70% mortality rate). Mortality drops to 40% in year two of life, then drops to 20% thereafter. A 10-year raptor is considered old. What kills them? disease, electrocution, rat poison, and collisions with cars, windows, wind turbines.
Hawk types
Buteos are soaring hawks (Red-tailed, Red-shouldered, Broad-winged, Swainson’s, Ferruginous, Rough-legged)
Accipiters are forest hawks who alternate flapping with gliding (Cooper’s, Sharp-shinned, Goshawk)
Falcons mostly flap, some gliding (American Kestrel, Merlin, Peregrine, Prairie falcons)
Osprey, Northern Harrier, Eagles (Bald & Golden), and White-Tailed Kites are in their own class. They mostly soar and glide with the exception of the Northern Harrier that glides, flaps and soars.
Large, dark raptors who soar: Turkey Vultures, California Condors
West County Hawkwatch has a website with raptor silhouettes and drawings useful for identifying raptors. They include a photo of GGRO’s yellow printed postcard with silhouettes that I keep in my backpack at all times — it’s so handy.
Volunteer with Hawk Hill
With only 4 staff members, GGRO relies heavily on volunteers to accomplish its mission. Hawk Hill is an open-air school where volunteers learn citizen science activities such as counting raptors, banding, and radio/satellite tracking. GGRO does cooperative research with University of California, Davis as well as welcoming visitors to Hawk Hill to observe their work and of course, the hawks.
GGRO bands an average of 1200 raptors per season across 4 sites. When they band a bird, it typically takes 20 minutes. To make the most of that time which is stressful for the bird, they are gathering critical research data for a lab in UC Davis including getting DNA samples to learn about feeding behavior.
Since 1983, GGRO has banded 45,000 hawks. Over that time 1600 bands have been recovered from dead birds. If you find a band, report it and take the band with you if you can so it’s not reported again. They have a low-tech way of tracking bands and cannot easily know if a band has already been reported.
Recent trends
GGRO has seen a substantial increase in Peregrine Falcons. Allen noted that shorebirds migrate faster when peregrines are migrating behind them. You don’t want to end up as dinner! Kestrels are declining which may be a result of the increase in peregrines which harass the kestrels. Jules Evens is tracking Osprey in North Marin and his data trends are the opposite of what Allen is seeing at Hawk Hill.
GGRO has learned that hawks migrate in every direction but mostly south in the fall. Some hawks don’t migrate at all but instead overwinter in the mild Bay Area.
Climate change and impacts on hawks
Shifting phenologies (life cycle events such as when birds breed, when they migrate, and where they go) are affecting migration patterns especially for those hawks whose prey is song birds such as Sharp-shinned hawks. GGRO has observed that “Sharpies” have delayed migration by 7.5 days over 26 years.
Atmospheric and weather patterns are changing. The ice melt in the Arctic is causing the jet stream to circulate in a wobbly pattern that allows cold air to escape the polar vortex and causes more erratic weather events. Read Rutgers University climate scientist Jennifer Francis’ article Evidence for a wavier jet stream in response to rapid Arctic warming.
What can you do to help raptors?
Get curious. Learn about raptors -- how to identify the species you see, what they eat, where they live. We protect the things we care about.
Don’t use poisons. They can easily get passed up the food chain from rat to raptor.
Be a role model. Value the natural landscape and let kids see you doing it.
The Golden Gate Raptor Observatory (GGRO) holds docent programs on Hawk Hill on Saturdays and Sundays in September and October. For details, visit http://www.parksconservancy.org/conservation/plants-animals/raptors/docent-programs.html
The power of volunteers
Besides being located in the beautiful Marin Headlands, the Marine Mammal Center and Golden Gate Raptor Observatory are both examples of small non-profit organizations with huge volunteer networks. They have mobilized their networks to accomplish a tremendous amount of conservation and science.