Humanity is greatly dependent on our ocean ecosystems. Oceans regulate our climate, protect our coastlines, and provide revenue, energy, food, recreation, and a sense of well-being. Even so, our activities individually and collectively on land and at sea may be threatening the integrity of the marine environment. In the past, most nations have attempted to manage human activities, and the resources they impact, one threat and one species at a time. More recently, however, the idea of holistic, ecosystem-based management in which multiple human activities are managed simultaneously has become the goal.

Researchers have started to quantify how human activities vary across the globe and have identified “hotspots” of human activities that threaten marine ecosystems. These spatial snapshots are useful for identifying vulnerable habitats and focusing limited management resources in areas that are most threatened. Snapshots, however, do not give us the full picture. Without an understanding of how human activities have been changing over time, it is difficult to determine what, if any, management actions are necessary to mitigate pressures that threaten ecosystem function. Surprisingly, such spatially explicit temporal views of human-caused pressures are rare. Our recently published article in Environmental Conservation, “The legacy of a crowded ocean: indicators, status, and trends of anthropogenic pressures in the California Current ecosystem,” sought to remedy this gap for the United States’ West Coast. In this analysis, we found that most indicators showed either significant short-term trends or their current status was at historically high or low levels. Indicators of inorganic and organic pollution and indicators related to marine transportation decreased during the recent global economic recession, while dredging activity and shellfish aquaculture increased. Indicators of seafood demand, shellfish aquaculture, nutrient input, sediment and freshwater retention and coastal engineering were above historic levels, while indicators of offshore oil and gas activity and related benthic structures were at historically low levels. These patterns emphasize the importance of monitoring changes in these pressures as economies recover, technologies improve and social norms change.

Not surprisingly, we also found that many pressures were highly correlated with one another – several increase or decrease at the same time— making it difficult to determine cause-and-effect relationships.  For many of these pressures, we do not fully understand the direct effect they have on the species, goods and ecosystem services that we care about. It is likely that the effect of individual pressures may not be strong, but the interactive and cumulative effects of multiple pressures acting simultaneously and over time may have significant effects on the ability of the ocean to meet our material and non-material needs. This is an important avenue of research that will be crucial for understanding the trade-offs associated with human activities that affect the marine environment.

This research is part of the U.S. National Oceanic and Atmospheric Administration’s (NOAA) Integrated Ecosystem Assessment of the California Current ecosystem. Integrated Ecosystem Assessments are designed to holistically determine the health of our ocean ecosystems and species that depend on them, including humans. Understanding the status and trends of threats to ocean health is a key step in our assessment. By integrating the threats generated by humans with the effects of environmental and social drivers, and linking this to the ecology of key species and communities, Integrated Ecosystem Assessments provide critical knowledge and tools to ensure the long-term sustainable management of our oceans.

Disclaimer: The views expressed above are those of the author and may not reflect those of the National Oceanic and Atmospheric Administration.

Image curtesy of Jameal Samhouri.

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