Geology and Ecology of National Parks

Ecology of Point Reyes National Seashore

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Northern California is known for its diverse wildlife and Mediterranean climate. This year-round mild climate allows for many types of ecosystems to thrive at Point Reyes National Seashore. Point Reyes National Seashore is a coastal park with wide ranges of ecosystems that demonstrate the complexity of California’s biodiversity. Point Reyes has five broad ecosystems: Forests; Ocean; Prairies and Grasslands; Sand Dunes; and Wetlands, Marshes, and Rivers.  

 

Forests

The Inverness Ridge runs through Point Reyes, splitting the area’s forests into two distinct types (1). Each of these forest types contains unique soil, plants, and wildlife. Each type of forest hosts different kinds of habitats.

A photo displaying a young Bishop Pine forest next to a photo displaying a mature Bishop Pine forest.

A young (left) and mature (right) bishop pine forest in Point Reyes National Seashore. NPS

(Public domain.)

Image: Western Gray Squirrel

A western grey squirrel eats an acorn in Yosemite Village, CA. This species also resides in Pt. Reyes.

(Credit: Alex Demas, USGS. Public domain.)

The northern portion of forest is a bishop pine forest. Bishop pine trees are fire dependent, meaning they require fire or high temperatures to successfully reproduce (2). They produce seed-containing cones annually, however these cones will only open and release the seeds upon burning or on a hot day. In younger bishop pine forests, trees grow packed densely together, however as these forests age, the trees self-thin and become more sparse (3). As of 2020, Point Reyes’ bishop pine forest is 25 years old, but scientists have found trees up to 71 years old. After about 80 years old, if they have not already succumbed to fire, bishop pines usually die of disease such as pine pitch canker (3). Other notable species in this forest are bay laurel, madrone, coast live oak, tanoak, and more. Wildlife found in this forest include western gray squirrels, jays, finches and sparrows.

 

 

 

 

 

A portion of the skyline of douglas fir trees in front of a light grey sky.

A Douglas fir mixed forest in Point Reyes, California. NPS

(Public domain.)

Did you know that Douglas fir trees can live to be over 500 years old (4)?  These trees are dominant in the southern portion of forest at Point Reyes. Douglas firs are fire resistant, meaning they will typically survive moderate intensity fires. In Coast Douglas fir trees, their strong, cork-like-bark protects the inside tissues of the tree during a fire, keeping the tree alive. Using fire records from the 19th and early 20th centuries, scientists estimate that fires used to burn about once every seven or eight years in Northern California’s Douglas fir forests. This burning was likely a forest management technique by the Miwok Tribe (4). Today, fires here average about once every 12 to 19 years. Similar to the bishop pine forests, other notable species are coast live oak, tanoak, and California bay. Douglas fir forests are not free from disease, either. Sudden Oak Death (SOD) is prevalent in this forest (5), creating more fuel for future forest fires as dead plant matter becomes flammable debris on the forest floor. Wildlife common in this kind of forest includes acorn woodpeckers, northern spotted owls, and black-tailed deer.

 

Northern spotted owl

A northern spotted owl perches on a tree branch.  USGS.

(public domain)

For more information about the forests of Point Reyes, or just California’s forests in general, see the Pt. Reyes Field Station and the USGS Climate Research and Development Program, which has resources about the potential effects of climate change on California’s forests.  

 

 

 

 

 

 

 

 

 

 

 

 

 

Oceans and Intertidal Zone

A photo of a tide pool.

A tide pool pictured in Point Reyes, California. Source: USGS 

(public domain)

The coast of Northern California, including Point Reyes National Seashore, sees diverse and robust marine life, due to upwelling (6). Upwelling is a process where the currents and wind along the coastline pull the surface layer of water out towards the open ocean, allowing the cold nutrient-rich water of the coastal deep ocean to rise to the surface and replace the previous surface water. This abundance of nutrients in the water supports the needs of underwater communities and promotes biodiversity.

According to the National Oceanic and Atmospheric Administration, the intertidal zone is “where the ocean meets land between high and low tides”(7). In the intertidal zone, sea life is especially diverse and abundant due to the varied combinations of light, nutrients, and oxygen available in the water (8). Organisms residing in any part of the intertidal zone need to be durable: they survive both underwater or in the open air, withstand crashing waves and wide temperature changes (8).

The intertidal zone splits into three separate zones, depending on how exposed or not each area becomes in different points of the tidal cycle. In the high intertidal zone, organisms are only underwater in high tide. This is the region farthest inland. Due to the constant crashing waves on the shore, you’ll find the toughest organisms here: rockweed, barnacles, turban snails, lined shore crabs, and more.

An orange sea star and a purple sea star lie next to barnacles in a tide pool at low tide in Olympic National Park.

Barnacles and sea stars in Olympic National Park in Washington attached to a rock at low tide. NPS

(Public domain.)

In the middle intertidal zone, organisms are exposed to the open air at least once per day, as the tides flow in and out over this area. Organisms found here might be softer-bodied than in the high intertidal zone: Sea stars, sea anemones, nudibranchs, chitons, mussels, barnacles, and more.

 

 

 

 

 

 

 

 

 

 

 

 

Dendronotid nudibranch on hydroids

Nudibranchs can be found in the intertidal zone of Pt. Reyes National Seashore. This image is from (from farther north, in Marrowstone, WA. USGS

(Credit: Nancy Elder, USGS, Western Fisheries Research Center, Marrowstone Marine Field Station. Public domain.)

In the low intertidal zone, organisms are only exposed to the open air in the extreme low tides (7). Spring tides-- also known as king tides-- occur when the earth, sun, and moon align during a full moon (9). This causes a greater gravitational pull on the earth’s oceans and creates more extreme tides. Life in this area is more abundant as it is usually underwater. Here, you will find organisms such as green giant anemones, nudibranchs, sea urchins, sea stars, bat stars, and more.

Anemones and associated anemonefish

Sea anemones live in the cool water of the intertidal zone. USGS

(Credit: Lukasz Niemoczynski, NJWSC. )

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Carbon’s Effects on the Ocean

Along the coast of Northern California, as elsewhere in the world, the ocean's chemistry is changing; this is known as ocean acidification (6). In this process, seawater becomes less basic as the ocean sequesters—or absorbs— excess carbon dioxide emitted into the atmosphere. As more carbon enters the atmosphere, the ocean absorbs more carbon. The chemical reactions that occur when the carbon dioxide reacts with the seawater result in a lowering of the ocean’s pH level (10), making it less basic. Ocean acidification affects the entire ocean, and especially organisms with shells. These organisms require carbonate to build their shells, however in less alkaline water, they tend to absorb less carbonate, which hinders their ability to solidify their shells.

 

Marine Mammals

In addition to the smaller marine species found in the intertidal zone, Point Reyes National Seashore is also home to some marine mammals. Mammals such as elephant seals and gray whales are a key feature of west coast marine life and differ from the types of mammals found in the east coast waters. Elephant seals spend the vast majority of their life out in the open ocean and can dive as deep as 2,000 feet below the water’s surface. Due to the way their body circulates oxygen, regulates heart rate, and compresses body fat when they dive, elephant seals are able to withstand the extreme conditions of the deep ocean while they dive for food (11). Gray whales migrate south from Alaska to Baja California to stay for the winter months, then migrate north back to Alaska to stay for the summer months. They usually pass through Point Reyes in January and again in March but can be seen in April and May as well. Adult gray whales weigh about 40 tons, and at birth, the calves (or baby whales) can weigh up to 1,500 pounds! (12).

Ocean fun facts (13):

  • Mussels, a bivalve, have strong byssal threads they use to attach themselves to rocks. Throughout the day, as waves crash in, mussels are constantly reattaching their threads and using a binding protein to the rock to keep themselves strongly anchored.
  • Sea stars eat mussels. They push their stomachs into their prey and digest their food after using their arms to open the mussel’s shell.
  • Nudibranchs eat sea anemones and save the stinging cells of the anemones for later! They then utilize these stored stinging cells for their own self-defense.
  • Some kinds of kelp can grow as fast as two feet per day!

For more information about ecology in the ocean, check out the USGS page about marine ecosystems. The USGS Pacific Coastal and Marine Science Center has many more resources about different aspects of ocean science and the USGS has an interesting video about research on ocean acidification in the Arctic Ocean. USGS has also published an article about the impacts of ocean acidification on marine life and ecosystems.

 

Prairies and Grasslands

Grasslands are ecosystems made up of grass or grass-like vegetation, free from trees or other woody plants. Prairies are ecosystems that consist of grasslands in regions with medium levels of rainfall and mild climates. The coastal grasslands at Point Reyes National Seashore are made up of both coastal prairie and agricultural ranchland. In Point Reyes National Seashore, the most abundant type of prairie is northern coastal prairie. This type of prairie is the most diverse prairie in North America, consisting of both Deschampsia coastal prairie and Danthonia coastal prairie (named according to the dominant species of grass present in each prairie). Coastal prairies are typically made up of perennial bunchgrasses (14). Perennial plants survive for many seasons as opposed to annual plants, that die every winter. Bunchgrasses are grasses that grow in bunches as part of separate growing points. Within Point Reyes, some species of native grasses are purple needle grass (Stipa pulchra), California fescue (Festuca californica), and California oatgrass (Danthonia californica) (14). Native grasses (and any native plants) are beneficial to ecosystems as they provide necessary food and shelter for native animals and insects and are well suited for the region’s climate and soil, promoting biodiversity and maintaining the integrity of an area’s natural history (15).

Alongside the native plants, Point Reyes has a long history of widespread non-native and invasive plant species. In the 1850s, farmers envisioned Point Reyes to be productive dairy land. In preparation to feed cattle, these ranchers began planting non-native grasses. While not all the introduced plants were invasive, such as Italian ryegrass (Lolium multiflorum) and clover (Trifolium sp.), many of the grasses planted by the ranchers were invasive (14). Invasive plants out-compete native plants, taking over landscapes (14). In Point Reyes, common invasive, non-native plants are velvet grass (Holcus lanatus), harding grass (Phalaris aquatica), and tall fescue (Festuca arundinacea) (16).

Eleven tule elk stand on a grass field in front of the ocean.

Eleven bull tule elk with velvet-covered antlers.

(Credit: Tim Burnot, NPS. Public domain.)

Since 2000, the National Park Service has made significant efforts to restore Point Reyes National Seashore prairies and grasslands to a more native-dominant state. Through a combination of burning, seeding, and mowing, the NPS hopes to encourage the growth of perennial native plants (14).

One of only two elk species native to California, Tule elk are endemic to California (only found here). After overhunting and the introduction of cattle throughout the 1800s, population sizes of Tule elk had dwindled so much that it was thought they had become extinct. Since 1847, Tule elk populations have slowly but steadily increased. Today there are almost 6,000 Tule elk in over twenty herds spread throughout California. At Point Reyes, Tule elk were removed in the 1850s when the dairy ranchers moved in. However in the 1970s, they were re-introduced to the Point Reyes region. Scientists have monitored the population at Tomales Point since 1990. In 2019, 445 individuals were counted in this herd (17). Read more about Tule elk from the National Park Service here.   

For information about the relationship between grazing animals and grasslands, visit the USGS Fort Collins Science Center website. The USGS Northern Prairie Wildlife Research Center has pages overviewing different aspects of prairie ecology.

 

Sand Dunes

Driftwood and sand dunes at Point Reyes National Seashore

Driftwood pictured in front of sand dunes in Point Reyes, California.  USGS

(Credit: Xochitl Rojas-Rocha, USGS Western Ecological Research Center. Public domain.)

Point Reyes National Seashore is home to a coastal sand dune ecosystem. While many other types of ecosystems are adapted to a more stable equilibrium, dune ecosystems are adapted to a state of instability. Sand dune ecosystems depend on the constant movement of the sand in order to be successful (18). The biodiversity of sand dune ecosystems is tied to the various successional stages possible. To reach these different stages, the dunes require disruption, usually wind, salt spray, burrowing by animals, or other forms of erosion or deposition (19). However, when invasive plant species, such as ice plant and European beachgrass, grow their roots down into the dunes, it secures the sand and prevents the necessary movement. This prevents the dunes from cycling through their different successional stages and stops natural sand deposition and erosion, which causes dunes to be taller and steeper than normal (19).  

 While sand is not a nutrient-dense growing medium for plants, some native dune plants have evolved an alternate methods of obtaining the ingredients necessary for a healthy plant life. For example, dune lupine harbors bacteria inside its roots. This bacteria converts nitrogen in the sand/soil and changes it into a usable structure for the lupine. This process is known as nitrogen fixation (20).

Endangered Species in Point Reyes’ Sand Dunes

Sand dunes at Point Reyes are home to 11 federally endangered species, including  Myrtle’s silverspot butterfly and the western snowy plover. Plovers are vulnerable to predation, as they lay their eggs in the open on beaches. About 50 years ago, western snowy plovers were known to nest at over 50 sites across California; today their nesting sites number in the 20s. Currently, there are about 2,500 western snowy plovers remaining, as opposed to the many thousands that once resided in California (18).

Invasive Species in Point Reyes’ Sand Dunes

 These sand dunes host a variety of invasive plant species that out-compete native plant species and heighten negative conditions for endangered animals. Invasive plants like iceplant and European beachgrass displace native species that typically provide nectar for Myrtle’s silverspot butterflies. These invasive plants spread across typical nesting areas for the western snowy plover and also provide hiding spaces for the bird’s predators (19).

For information about the formation and types of sand dunes, see this fact sheet from research on the Navajo Nation dunes and this USGS page on types of sand dunes on Earth and Mars.

 

Wetlands, Marshes, and Streams

Image: Water Quality Sampling

A scientist measures water quality at a wetland in Point Reyes, California. USGS

(Credit: Toni Russel, USGS. Public domain.)

Point Reyes National Seashore has several wetland ecosystems: estuaries, salt marshes, swamps, and riparian habitats. Estuaries are areas where freshwater streams or rivers meet saltwater. Estuaries are known for being spawning habitats for crabs and fish (21) and also serve as “pit-stops” for migratory birds, like ducks or shorebirds. For more information on estuaries, take a look at this page from the USGS. Salt marshes are a type of wetland that occur in saline environments (areas with salt water, like estuaries). Salt marsh plants have adapted to salty water. The grasses and plants in salt marshes have short stems and small leaves, which allows them to expel more excess salt per unit volume than would larger leaves and stems. Swamps are a type of freshwater wetland that is characterized by surrounding forests and relatively low drainage. Riparian habitats are located along the sides of streams and lakes and typically contain plants adapted to a great amount of water. Wetlands provide necessary ecosystem services (21). For example, all of the wetland types mentioned here slow, absorb, and store potential flood waters and improve water quality by filtering sediments and pollutants.

Point Reyes contains many small streams and creeks. These streams and creeks provide freshwater environments and nutrients for birds, fish, amphibians, bugs, and aquatic invertebrates, animals without a backbone (22).

 

Endangered Species in Point Reyes’ Wetlands

The Point Reyes population of coho salmon is at risk of becoming extinct (23). Currently, their populations sit at about 1% of what they once were (23). Early on in their life, coho live in freshwater streams and wetlands, then they swim out to the open ocean for their adult lives. Because they inhabit two different habitats, any environmental change for either habitat affects coho populations. Ocean acidification and shrinking freshwater wetlands are two such changes. Because of this life history characteristic of living in both freshwater and the ocean, coho salmon are considered an indicator of ecosystem health. If a healthy population of coho salmon lives in streams and the ocean, it is indicative of a healthy ecosystem (23) For more information about coho, check out this information from the USGS Western Fisheries Research Center.

For more information about wetlands and other aquatic ecosystems and the science currently happening in these ecosystems, check out the USGS Wetland and Aquatic Research Center.

 

Sources

  1. https://www.nps.gov/pore/learn/nature/forests.htm
  2. https://www.nps.gov/pore/learn/management/firemanagement_fireecology_vegtypes_bishoppine.htm
  3. https://www.nps.gov/pore/learn/nature/plantcommunity_pineforest.htm
  4. https://www.nps.gov/pore/learn/management/firemanagement_fireecology_vegtypes_douglasfir.htm
  5. https://www.nps.gov/pore/learn/nature/plantcommunity_firforest.htm
  6. https://www.nps.gov/pore/learn/nature/oceans.htm
  7. https://oceanservice.noaa.gov/facts/intertidal-zone.html#:~:text=The%20intertidal%20zone%20is%20the,extend%20for%20hundreds%20of%20meters
  8. https://www.nps.gov/rlc/pacificcoast/intertidal-ecosystems.htm
  9. https://oceanservice.noaa.gov/facts/springtide.html
  10. https://www.nps.gov/pore/learn/nature/ocean_acidification.htm
  11. https://www.nps.gov/pore/learn/nature/elephant_seals.htm
  12. https://www.nps.gov/pore/learn/nature/gray_whales.htm
  13. https://www.nps.gov/pore/learn/nature/intertidal.htm
  14.  https://www.nps.gov/pore/learn/nature/prairies.htm
  15. https://www.fs.fed.us/wildflowers/Native_Plant_Materials/Native_Gardening/index.shtml
  16. https://www.nps.gov/pore/learn/management/firemanagement_fireecology_vegtypes_grasslands.htm
  17. https://www.nps.gov/pore/learn/nature/tule_elk.htm
  18. https://www.fws.gov/refuge/humboldt_bay/wildlife_and_habitat/dunesrestoration.html
  19. https://www.nps.gov/pore/learn/nature/sanddunes.htm
  20. https://www.fws.gov/refuge/Humboldt_Bay/wildlife_and_habitat/YellowBushLupine.html
  21. https://www.nps.gov/pore/learn/nature/wetlands.htm
  22.  https://www.nps.gov/pore/learn/nature/rivers.htm
  23. https://www.nps.gov/articles/coho-habitat-and-climate.htm

 

Map of Point Reyes Vegetation 

 

USGS Pt. Reyes Field Station: https://www.usgs.gov/centers/werc/science/pt-reyes-field-station?qt-science_center_objects=0#qt-science_center_objects