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Global climate change is happening right now, and it is one of the most pressing problems of our modern world. When humans began burning fossil fuels (1) (coal, oil, and gas) for energy during the Industrial Revolution in the late 1700s, and especially in the early 1800s, we also began emitting greenhouse gases (notably carbon dioxide, or CO2), which trap heat within the Earth’s atmosphere. Ever since we as humans have been causing a man-made global greenhouse effect, or planetary warming, that has been intensifying alongside our use of fossil fuels ever since, with a particular acceleration after 1985. Since 1850, the global average surface temperature has increased (2) by about two degrees Fahrenheit (°F), with the ten warmest years all occurring (3) since 2010, and 2023 as the hottest year in history. All of the extra heat trapped by greenhouse gasses that we emit by using fossil fuel-generated electricity, gas-powered cars, and more, is melting ice caps, warming and acidifying oceans, making sea levels rise, causing the Earth’s sixth mass extinction, and bringing about potentially dangerous regional and seasonal shifts in climate and weather across the globe.

Graph of global fossil fuel consumption from 1800-2022, measured in terawatt-hours (TWh) of primary energy consumption. Coal (blue) begins at 0 TWh in 1800, and then rises to ~2,000 TWh in 1850, ~10,000 TWh in 1900, ~15,000 TWh in 1950, ~30,000 TWh in 2000, and ~45,000 TWh in 2022. Oil (red) begins at 0 TWh in 1800-1900, and then rises to ~5,000 TWh in 1950, ~25,000 TWh in 2000, and ~50,000 TWh in 2022. Gas (green) begins at 0 TWh from 1800-1950, and then rises to ~20,000 TWh in 2000 and ~35,000 TWh in 2022.

Global fossil fuel consumption, 1800-2022.

Source: Our World in Data (4)

The diverse natural landscapes, rugged coastlines, bay and wetlands, wild and scenic rivers, iconic redwood forests and native wildlife, and coastal and inland communities of California’s North Coast — which encompasses Mendocino, Humboldt, Del Norte, Lake, Trinity and Siskiyou Counties — are threatened by numerous climate change impacts. We also have a responsibility to seize our unique local opportunities to slow climate change and mitigate its impacts.

Rising Temperatures

Average daily temperatures across the North Coast have increased less than 1 °F over the past century, with a current annual average maximum temperature of 60-64 °F. Coastal areas near the temperature-moderating Pacific Ocean average maximum temperatures of 60-70 °F, while inland areas average maximum temperatures of 70-90 °F. Average annual maximum temperatures across the region are projected to increase 5-9 °F in the next 75 years before the end of the 21st century, with the largest increases in inland areas in Siskiyou and Trinity Counties, where the hottest days of the year could exceed 105 °F. (pg. 15-18) (5)​

Map of average historical temperature on the hottest day of the year on the North Coast from 1976-2005, adjacent to maps of the projected average temperature on the hottest day of the year under a stabilization (RCP 4.5) emissions scenario and a business-as-usual (RCP 8.5) emissions scenario between 2070-2100.

Map of average historical temperature on the hottest day of the year on the North Coast from 1976-2005, adjacent to maps of the projected average temperature on the hottest day of the year under a stabilization (RCP 4.5) emissions scenario and a business-as-usual (RCP 8.5) emissions scenario between 2070-2100.

Source: Grantham 2018, pg. 18 (5)

​​The ocean has absorbed more than 90% of the extra heat energy (19) caused by climate change. The average global sea surface temperature increased by approximately 2.8°F (19) from 1901 to 2020 with that number expected to continue to rise as global warming worsens. Here on the North Coast, an ocean heatwave nicknamed "the Blob" has given us a sneak peak at what impacts future ocean warming will have on marine ecosystems. Researches investigating the impacts of the "the Blob" (20) found that certain species including Dungeness crab, mussels, salmon, and baleen whales would suffer under warmer conditions while other species including tuna, rockfish, and toxic phytoplankton benefit.​

Organisms observed to be positively and negatively impacted by the Warm-Water Anomaly

Organisms observed to be positively and negatively impacted by the Warm-Water Anomaly (WWA). Negatively affected organisms are labeled as "Losers" (left column), while organisms positively affected are labeled as "Winners" (right column). Organisms are presented in both columns from lower (top of the column) to higher (bottom of the column) trophic levels.

Source: Cavole et al (20)

Precipitation Whiplash

With its characteristic Californian Mediterranean climate, the North Coast usually gets most of its annual precipitation from a few large storms (the most intense in the State) between November and March. In the context of climate change, total annual precipitation across the region is not projected to change significantly, but storm events will likely become more intense in increasingly shorter wet seasons (i.e. December to February) by the end of the 21st century, which will increase the frequency and extent of flooding in low-lying areas, particularly along the coast where flood risk will be enhanced with rising sea levels. The North Coast will likely also experience more extreme, prolonged dry seasons under a new climate regime termed “precipitation whiplash,” which is characterized by frequent, dramatic swings between wet and dry years and seasons. An “average” rainfall year will become less common. Due to rising temperatures and more intense, punctual storms, it is also projected that less precipitation will fall as snow and total snowpack will dwindle, further exacerbating dry spells. (pg. 19-20) (5)​

Drought

While drought is a common, recurring event throughout California, recent studies have found that current and future increases in temperature, regardless of changes in precipitation, increase the frequency of longer, more extreme droughts statewide — especially when paired with “precipitation whiplash.” Scientists predict that severe droughts that now occur only once every 20 years will occur once every 10 years by the end of the 21st century, and once-in-a-century droughts will occur once every 20 years. For example, the 2012-2016 California drought, which led to the largest moisture deficits in the last 1,200 years, was likely caused by a “ridiculously resilient ridge” of high-pressure air in the North Pacific that steered storms north, away from California, and is thought to have been caused by melting Arctic sea ice and related sea surface temperature anomalies — both direct results of global warming and climate change. (pg. 21 & 24) (5)​

Loss of Snowpack

Snowpack across California is projected to decline due to regional warming, regardless of changes in precipitation. Snowpack on April 1st in areas above 3,000 feet in elevation declined from 60% in 1951-1980 to 50% in 1981-2010, with the greatest loss occurring in the Klamath-Siskiyou Mountains of the North Coast. Under a warm, moderate rainfall climate scenario, snowpack on April 1st is projected to decline to 11% by the late 21st century. An even greater decline is projected under warm, low rainfall climate scenarios. (pg. 21) (5)​

Map of historical and projected footprint of April 1 snow cover, with gray showing "No Historical April Snow," red showing "Snow Present Historically (1951-1980)", orange showing "Snow Present Recent (1981-2010)", yellow showing "Snow Present Mid-Century (2040-2069)", and white showing "Snow Present End of Century (2070-2099)."

Historical and projected footprint of April 1 snow cover.

Source: Grantham 2018, pg. 21 (5)

Soil Aridity

Rising temperatures, precipitation whiplash, shorter wet seasons, and loss of snowpack are collectively projected to increase the frequency and magnitude of soil water deficits, also known as soil aridity (or dryness), on the North Coast — which translates to stress on plants, and their consequent death, migration, or extinction. Regardless of projected precipitation changes, scientists predict that most of the North Coast will suffer from soil aridity that will cause difficulties for the survival and persistence of local plant communities. (pg. 22) (5)​

Wildfire

Fire ecology on the North Coast is just as naturally complex and diverse as the region’s climate and biodiversity, which varies, especially east-to-west, based on proximity to the Pacific Ocean. In general, rising temperatures are projected to lengthen the North Coast’s fire season, especially in higher elevation sites with decreasing snowpack and consequently drier conditions. Lightning strikes historically cause the most wildfires in California, and such fires are likely to become more frequent during a longer dry, fire-prone season with more dead, dry plants to serve as fire fuels. Human-ignited wildfire is also predicted to become more regular in more populated areas of the North Coast. (pg. 23) (5)

Streamflow

Freshwater habitats, including rivers and streams, are especially vulnerable to the rising temperatures and increased precipitation variability caused by climate change. Water quantity, or streamflow, in North Coast rivers and creeks has declined consistently over the past 50 years — especially during the dry season between August and November. Regardless of precipitation changes, scientists predict that rivers and streams across the North Coast will continue to experience significantly lower flows as a result of climate change in the next 75 years, especially during the summer months, due to increasing evapotranspiration (combined water loss from soil evaporation and plant leaf transpiration). Consistent with “precipitation whiplash,” increases in drought frequency and intensity are projected to further decrease water quantity, with the lowest streamflow in each decade projected to be 30-40% lower than average historical conditions by the end of the century. Peak flows in the winter are also likely to increase with more intense storm events. (pg. 23-24) (5)

Low flows and green algae in the Shasta River.

Low flows and green algae in the Shasta River.

Source: Nick Joslin / Mount Shasta Bioregional Ecology Center

Longer, more intense dry seasons will be challenging and potentially deadly to cold water-dependent aquatic species, such as imperiled native salmon and steelhead trout. A vulnerability assessment (6) of the State’s fish found that 82% of native species, versus only 19% of non-native species, are vulnerable to climate change — suggesting that rivers and streams will become increasingly dominated by non-native fish species. Poor water quality from excessive sediment is already an issue for North Coast waterways, many of which are listed under section 303(d) of the federal Clean Water Act, and further disturbance events caused by climate change, including heavy rainfall, floods, wildfires, and debris flows, are projected to only worsen the problem. (pg. 34-35) (5)

Fog Dynamics

Coastal fog is a defining feature of the North Coast that occurs year-round, and is practically synonymous with the “redwood curtain.” Coastal fog forms when a layer of moist air is trapped between the cold Pacific Ocean and a layer of warm, dry air from the upper atmosphere, gradually loses its heat to the ocean, and condenses into fog droplets. Areas exposed to northwesterly winds experience the most summertime fog, whereas areas sheltered from that wind get the least fog; for example, Eureka is foggy for an average of 14 hours per day in the summer, while Shelter Cove averages less than two hours of summer fog daily. Coastal forests obtain up to a third of their water from fog, and many fog-dependent plants, including coast redwoods (Sequoia sempervirens), can absorb water directly through their leaves. Fog drip supports understory plants and provides water to streams that would otherwise dry up during the dry season. Summer fog shades and cools coastal areas and reduces the rate of evapotranspiration, so that plants use less water from the soil. Decreases in summertime fog result in higher temperatures, reduced summer streamflows, more soil aridity, increased wildfire risk, greater electrical demands for cooling, and heat-related human health risks.

Map of average fog cover in hours per day in the North Coast region from 1999-2009. Areas colored in dark blue (such as Rio Dell and Eureka) experience => 13 hours of fog and low cloud cover per day; areas colored gray-blue (such as Fort Bragg, Trinidad, and Redway), experience 8-12 hours of fog and low cloud cover per day; areas colored light blue (such as Crescent City and Klamath) experience 5-8 hours of fog and low cloud cover per day; areas colored yellow experience 4 hours of fog and low cloud cover per day; areas colored orange (such as Laytonville) experience 2-3 hours of fog and low cloud cover per day; and areas colored red experience <2 hours of fog and low cloud cover per day.

Average fog cover in hours per day in the North Coast region (1999-2009).

Source: Grantham 2018, pg. 24 (5)

While summer fog is diminishing around the world due to climate change, trends on the North Coast are inconclusive, largely because the ocean-atmospheric processes that affect fog are not fully understood. For instance, climate change-driven rising temperatures can cause inland incursion of coastal fog due to greater temperature differentials between coastal and inland areas, but studies have also shown that days with high inland temperatures and strong updrafts of warm air are less likely to have coastal fog. Also, high inland temperatures strengthen onshore sea breezes, and increased winds — which are projected globally under climate change — can increase the upwelling of cold ocean water that causes condensation and coastal fog. However, not all cold sea surface temperature conditions produce fog, suggesting that atmospheric dynamics are also significantly at play. More research is needed to understand how fog dynamics on the North Coast will be influenced by climate change, with a particular focus on shifts in global air circulation patterns. (pg. 24-26) (5)

Sea Level Rise

Climate change is driving global sea-level rise at a global average rate of about 0.14 inches per year (7) by warming ocean water, which then expands, and melting glaciers and ice sheets, which then add water to the ocean. As the Earth heats up, sea-level rise will continue to threaten coastal communities and infrastructure with more frequent flooding, and then permanent inundation of low-lying areas and erosion of coastal features. Greenhouse gasses that we have already emitted will lead to a global sea level in 2050 that is at least 12 inches higher (8) on average than a 1991-2009 baseline. Beyond 2050, however, sea-level rise projections vary based on the extent of our greenhouse gas emissions and associated global warming — thus, we have the power to slow down this trend. Scientists project that significantly reducing our use of fossil fuels and carbon dioxide emissions could limit additional sea-level rise to 2.4 to 4.5 feet by 2100, but without meeting those goals, global sea level could rise by up to 8 feet by 2100 (30-40 times faster than we have experienced in the last century).

Projections of sea-level rise on the North Coast are complicated by varying rates of vertical land movement, which are driven by plate tectonics. Most of coastal California, including Crescent City, is interseismically uplifting faster than the rate of global sea-level rise, which results in a negative local rate of sea-level rise (-0.65 millimeters per year). By contrast, Wigi (9)/Humboldt Bay has the highest local rate of sea-level rise in California (0.2 inches per year) because of land subsidence around the bay. (pg. 26-27) (5)

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By 2060, the sea level of Wigi/Humboldt Bay is expected (10) to be about 1.5 to 2 feet higher than it was in the year 2000. Engineering higher dikes might seem like an obvious fix — but this won't solve the problem because as the sea rises, groundwater behind dikes will also continue to rise.

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While themselves unrelated to climate change, king tides (11) — the highest tides of the year that average 1-2 feet higher than average high tides — are a useful way to approximate how high regular tides are expected to be over the next few decades due to sea-level rise. King tides in Wigi/Humboldt Bay in January 2024 showed (12) waves engulfing land that is normally dry. Understanding the future impacts of sea-level rise is the first step toward adapting to these changes. You can contribute to the California King Tides Project (13) by *safely* taking and sharing photos of king tides in your area.

Map of predicted inundation of Wigi/Humboldt Bay with 3 ft of sea level rise.

Predicted inundation of Wigi/Humboldt Bay with 3 ft of sea level rise.

Source: County of Humboldt (14)

Plants & Forests

Thanks to diverse geology created by tectonic processes likened to dragging a pizza under a door, the North Coast is ecologically and botanically diverse — including coast redwood (Sequoia sempervirens) and Sitka spruce (Picea sitchensis) forests along the coast, hardwood forests and shrub plant communities inland, and high elevation subalpine forests in the Klamath-Siskiyou Mountains.

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Coast redwoods and other fog-dependent coastal species may suffer significant climate change impacts, especially if coastal fog penetration into interior river valleys declines. Longer, more intense fire seasons are projected to reduce forest densities and potentially shift several landscapes to early seral conditions. Grand fir (Abies grandis) and Sitka spruce, with their low fire tolerances, are more susceptible to this element of climate change than the fire-adapted coast redwood.

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Mixed evergreen and montane conifer forests, including Douglas fir (Pseudotsuga menziesii), tanoak (Notholithocarpus densiflorus), California bay laurel (Umbellularia 

Map of vegetation types and land cover in the North Coast region.

Vegetation types and land cover in the North Coast region.

Source: Grantham 2018, pg. 29 (5)

californica), and Pacific madrone (Arbutus menziesii), have moderate climate resilience with adaptations to relatively broad temperature and latitudinal gradients. Hardwood species are generally adapted to fire, and the biggest predicted threat to these widely-distributed tree species is the climate water deficit projected for the inland regions of the North Coast.

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Oaks, which can tolerate broad precipitation and temperature regimes, may actually benefit from the hotter, drier conditions brought about by climate change and begin recolonizing lands encroached on by conifers during wetter periods.

Coast live oak (Quercus agrifolia).

Coast live oak (Quercus agrifolia).

Source: Ken Kistler (15)

The Klamath Mountains are one of the most botanically diverse temperate regions in the world, with numerous rare and endemic species that are especially vulnerable to changes in climate because of their often small, isolated, and geographically restricted populations. These high elevation forests and plant communities of the North Coast likely face the greatest level of threat from climate change. (pg. 29-31) (5)

Wildlife

The North Coast is home to diverse wildlife species, many of which are endemic, rare, threatened, and/or endangered. Projected changes to plant communities and water availability due to climate change will shift the spatial and temporal distribution of habitat, food, and water for wildlife. Extreme weather events, including wildfires and floods, have already and will continue to impact wildlife populations. Studies have shown that climate change will likely enhance the spread of disease and invasive species that will affect and displace native wildlife. Wildlife species moving to new areas will also encounter novel species and potentially increased human-wildlife conflict, both posing potential significant impacts to wildlife populations and ecosystems (pg. 32-33) (5). On their website Survival by Degrees (17), the National Audubon Society states that under a scenario of 3.0 degrees of global warming, 40 bird species in Humboldt County would be highly vulnerable due to climate change. Marine species are expected to be seriously negatively impacted by rising ocean temperatures. During an ocean heat wave known as "the blob," scientists documented (18) range displacement for 57 alga, bird, cnidarian, crustacean, ctenophore, echinoderm, fish, mollusk, marine mammal and tunicate species. 

Coastal Wetlands & Estuaries

Sea-level rise is a formidable threat to coastal wetlands and estuaries, as well as the species and human communities that inhabit them. Under high sea-level rise scenarios, scientists project that all coastal marsh habitats in Northern California and Southern Oregon will become inundated and transform into mudflats. Former wetland habitats currently sequestered behind dikes or levees may become inundated by sea-level rise and partially replace habitat lost farther offshore — but not without detriments to infrastructure and agricultural lands. (pg. 38) (5)

Rangelands & Agriculture

Agricultural and rangelands on the North Coast are expected to be significantly impacted by more variable, unpredictable precipitation and soil aridity due to climate change. Less reliable precipitation events and drier soils will make it harder to meet water demands for crops and pastures. Rangeland quality is also projected to decline due to the encroachment of hardwood forests and rangeland weeds, such as yellow star thistle (Centaurea solstitialis), barbed goatgrass (Aegilops triuncialis), and medusahead (Taeniatherum caput-medusae), that favor hot, dry conditions. Wildfire risk will also rise with increased fuel loads on traditionally grass-dominated ecosystems.

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On prime agricultural lands, crop diversities may increase with rising temperatures and a longer growing season, but decreasing fog and precipitation might make irrigated beef and dairy operations more reliant on silage corn. Prime agricultural lands and dairy operations

Yellow starthistle (Centaurea solstitialis).

Yellow starthistle (Centaurea solstitialis).

Source: Washington State Noxious Weed Control Board (16)

around Wigi (9)/Humboldt Bay and the Eel River delta are also threatened by sea-level rise, which could increase the frequency of flooding, especially if levees fail. Even with levees in place, however, low-lying areas will still be susceptible to flooding from groundwater rising to the surface as driven by sea-level rise.

 

Recent regulatory changes are projected to influence the North Coast’s cannabis industry more than climate change. Cannabis farming is projected to continue on the North Coast, but will likely move from remote areas to more traditional agricultural lands at lower elevations, greenhouses, or indoor grow operations, in response to State legalization of recreational cannabis use and consequent steep increases in supply and decreases in market value.


Vineyards on the North Coast are projected to suffer from the longer dry summer season, increased temperatures, and greater frequency of drought years expected under climate change. (pg. 39-40) (5)

References

  1. Ritchie, H. and Rosado, P. (2024, January). Fossil fuels. Our World in Data. https://ourworldindata.org/fossil-fuels 

  2. Lindsey, R. and Dahlman, L. (2024, January 18). Climate Change: Global Temperature. National Oceanic and Atmospheric Administration. www.climate.gov/news-features/understanding-climate/climate-change-global-temperature

  3. National Oceanic and Atmospheric Administration. (2024). Temperature Anomaly: Yearly (NOAA) - 1850 - Present. Science on a Sphere. https://sos.noaa.gov/catalog/datasets/temperature-anomaly-yearly-noaa-1850-present/ 

  4. Our World in Data. (n.d.). Global fossil fuel consumption [Chart]. https://ourworldindata.org/grapher/global-fossil-fuel-consumption

  5. Grantham, Teodore (University of California, Berkeley). 2018. North Coast Summary Report. California’s Fourth Climate Change Assessment. Publication no. SUM-CCC4A-2018-001. www.energy.ca.gov/sites/default/files/2019-11/Reg_Report-SUM-CCCA4-2018-001_NorthCoast_ADA.pdf

  6. Moyle, P., Kiernan, J.D., Crain, P.K., and Quiñones, R.M. (2013, May 22). Climate change vulnerability of native and alien freshwater fishes of California: a systematic assessment approach. PLoS One, 8(5). doi.org/10.1371/journal.pone.0063883

  7. Cybersecurity & Infrastructure Security Agency. (n.d.). Sea Level Rise. www.cisa.gov/topics/critical-infrastructure-security-and-resilience/extreme-weather-and-climate-change/sea-level-rise

  8. Sievanen, Leila*, Phillips, Jennifer*, Charlie Colgan, Gary Griggs, Juliette Finzi Hart, Eric Hartge, Tessa Hill, Raphael Kudela, Nathan Mantua, Karina Nielsen, Liz Whiteman. 2018. California’s Coast and Ocean Summary Report. California’s Fourth Climate Change Assessment. Publication no. SUMCCC4A-2018-011. (*shared frst authorship) www.energy.ca.gov/sites/default/files/2019-11/Statewide_Reports-SUM-CCCA4-2018-011_OceanCoastSummary_ADA.pdf

  9. Wiyot Tribe. (n.d.). Wiyot Placename Video. www.wiyot.us/162/Wiyot-Placename-Video

  10. Humboldt Waterkeeper. (2024). Sea Level Rise. https://humboldtwaterkeeper.org/climate-change-impacts-sea-level-rise

  11. California Coastal Commission. (2019). About the King Tides Project. California King Tides Project. www.coastal.ca.gov/kingtides/learn.html

  12. Quezada, J. (2024, January 26). Photos | King tides hit Humboldt Bay. Times Standard. www.times-standard.com/2024/01/26/photos-king-tides-hit-humboldt-bay/

  13. California Coastal Commission. (2019). Take and Share King Tides Photos. California King Tides Project. www.coastal.ca.gov/kingtides/participate.html

  14. Humboldt County Civil Grand Jury. (2022). The Sea Also Rises. County of Humboldt. https://humboldtgov.org/DocumentCenter/View/107182/2-The-Sea-Also-Rises?bidId=

  15. Kistler, K. (n.d.). Oak Tree and Sun [Photo]. Public Domain Pictures. www.publicdomainpictures.net/en/view-image.php?image=117131&picture=oak-tree-and-sun 

  16. Washington State Noxious Weed Control Board. (n.d.). Yellow starthistle. www.nwcb.wa.gov/weeds/yellow-starthistle

  17. Audubon. Vulnerable Birds in Humboldt County. https://www.audubon.org/climate/survivalbydegrees/county?zipCode=95503

  18. Sanford, E., et al. Widespread shifts in the coastal biota of northern California during the 2014–2016 marine heatwaves. Scientific Reports 9, no. 1 (2019): 4216. https://www.nature.com/articles/s41598-019-40784-3

  19. Ross, L. and Bradford, N. (2024, May 30). A Warming Ocean. National Environmental Education Foundation. https://www.neefusa.org/story/water/warming-ocean

  20. Cavole, Letícia M., et al. Biological impacts of the 2013–2015 Warm-Water Anomaly in the Northeast Pacific: Winners, Losers, and the Future. Oceanography 29.2 (2016): 273-285. https://tos.org/oceanography/article/biological-impacts-of-the-20132015-warm-water-anomaly-in-the-northeast-paci

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