Historical kelp forests in California over multiple centuries

Kelp forests have deteriorated globally due to anthropogenic stressors. There is an urgent need to extend baselines, to understand the processes that underlie the persistence and recovery of kelp forests, and to distinguish the normal range of ecosystem variability from more extreme changes. Using a mixed-method, historical ecology approach we integrate archival data, oral histories, and contemporary ecological data to examine the dynamics of kelp forests over a multi-decadal to multi-century time period in central California. We focus on sea otters, sunflower seastars, sea urchins, kelp cover, kelp species dynamics, and climate. From 1826 to 2020 kelp was highly variable. There were seven periods of low kelp cover and two periods of exceptionally low kelp cover (1896-1899; 2014-2016) following El Niño-Southern Oscillations (ENSOs). Exceptionally low kelp cover did not occur when two predators – seastars and sea otters – were present. In all cases, kelp recovered following times of extr..., Study Area
Our research focused on kelp forest ecosystems in central California, USA (here, Año Nuevo (37°07'35.4\"N, 122°19'35.4\"W) in the north to Big Sur (36°06'16.2\"N, 121°37'19.8\"W) in the south. This cold water, upwelling-driven ecosystem is characterized by high biodiversity. The social-ecological history of central California has been documented for over two hundred years by historical and contemporary sources due to the region’s history of Tribal nations, exploration, European colonization, maritime trade, and Western science. We divided central California into three regions, north to south: Santa Cruz, Monterey Peninsula, and Big Sur.
Data Sources
To identify historical baselines and longitudinal dynamics of kelp forest ecosystems, we assembled a multi-decadal to multi-century dataset that integrated historical and contemporary information focused on central California largely from the early 1800s onward. We evaluate trends in the relative abundance of sea otters (Enhydra lutri..., , # Historical kelp forests in California over multiple centuries

[https://doi.org/10.5061/dryad.xpnvx0khq](https://doi.org/10.5061/dryad.xpnvx0khq)

For this research, we integrated hundreds of datasets to look at the historical changes in kelp forests through time. The data sets we considered ranged from 1602 to 2020.

| FILE | TYPE | DESCRIPTION | YEARS |
| :---------------------------------------------- | :----------------- | :------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | :-------- |
| coding\_themes\_categories\_oral\_histories.csv | analysis | themes used to code oral history data ...