Stream Health Correlated with Human Well-being and Demographics in Virginia

USGS Cooperative Research Unit Corner

Stream Health Correlated with Human Well-being and Demographics in Virginia

Relationships between human well-being (HWB) and ecosystem health (EH) are best understood via approaches coupling natural and social sciences. The Virginia Cooperative Fish and Wildlife Research Unit, a program in the Ecosystems Mission Area at the U.S. Geological Survey, is leading an interdisciplinary team of scientists from Virginia Tech to explore HWB-EH relationships and design follow-up studies to identify mechanisms driving those relationships.

Virginia stream

The assumption that healthy ecosystems benefit people commonly justifies biodiversity conservation and environmental protection, especially in managing water resources. A clearer understanding of the linkages between HWB and EH could help managers of natural resources and human health reach shared goals. Furthermore, broad recognition of the societal benefits of healthy ecosystems could bolster public support for environmental protection and facilitate management that promotes positive interactions between people and nature.

Human health (physical and mental) is strongly linked to the many benefits provided by healthy ecosystems (“ecosystem services”). Those benefits are commonly related to water and food supplies, psychological outlook, cognitive performance, and disease rates. Motivations to protect EH often reflect a person’s sense of place and/or hope for the future, which stem from community-specific histories and cultures. Thus, what “counts” as a healthy ecosystem varies among communities.

Many indicators are used to characterize HWB and EH. Indicators of HWB range from mortality rates to perceptions of personal safety to levels of community engagement; indicators of EH range from contaminant burdens in wild animals to species diversity to rates of nutrient cycling. The fact that health of individuals (human versus nonhuman, respectively) is central to both concepts implies some indicators may be correlated.

Key challenges to understanding HWB-EH relationships include disagreements on how to measure HWB and EH, as well as community-specific variation in demographic and socioeconomic conditions, which can promote inequalities in HWB. Poor and/or minority communities commonly bear greater exposures to polluted water. Harmful exposures can come from the water itself or from eating contaminated fish or shellfish.

Publicly available data on Virginia’s population and stream health provide rich sources of information to explore HWB-EH relationships and may shed light on U.S.-wide patterns. Virginia is racially diverse and includes counties representing national extremes in human health and wealth. Environmental quality ranges widely from western Virginia’s mountains to the Atlantic coast. Stream health is a good proxy for EH because surface waters are widespread, important points of human contact for pollutants, as well as major sources of ecosystem services.

The research team recently used data for Virginia counties to examine pairwise correlations among two inversely related indicators of stream health, thirteen indicators of HWB, and four demographic metrics. Indicators of stream health included the Virginia Stream Condition Index (VSCI) and the percentage of stream kilometers with a fish-consumption advisory (%FCA). HWB indicators represented the domains of health, education, safety and security, and living standards. Demographic metrics included population density, percentage White (%White), percentage foreign-born, and median age.

Both VSCI and %FCA were correlated with multiple demographic and HWB indicators. VSCI was higher in counties with higher %White, higher median age, and lower population density. Obesity prevalence, cancer and infant mortalities, violent and property crimes, and food insecurity were higher in counties with lower VSCI scores. VSCI was most strongly correlated with %White (positively) and violent crime rate (negatively). %FCA was higher in counties with higher diabetes prevalence and mortality, disability prevalence, overall mortality, violent and property crimes, and food insecurity, but lower in counties with greater median age, household income, and home value. %FCA was most strongly correlated with overall mortality (generally highest in coalfield counties).

Causal linkages between HWB and EH – not just correlations – are critical for informing management of ecosystem and/or public health. Though these findings highlight topics for future study (e.g., links between EH and racism, links between contaminants and mortality), understanding causation will require more refined analyses to reveal the specific pathways and feedbacks linking HWB and EH. For example, a causal link from %FCA to human mortality would require confirmation that people eat enough local contaminated fish to shorten their lives. To inform management, scientists need to know more about how people interact with nature in ways that affect their health.

Demographic factors such as race complicate our understanding of HWB-EH relationships. Current spatial disparities in the environmental quality experienced by racial groups may reflect differences in political engagement, socioeconomic influence, and/or settlement history. The strength of the correlation observed between VSCI and %White was striking despite limitations of the analysis, suggesting it is worth exploring further. Given extensive past research demonstrating that minorities in other regions are more likely to live in polluted environments, and consequently suffer impaired health, examining the factors underpinning the findings from Virginia seems like a top research priority.

Although intriguing, these findings do not allow inferences regarding which factors drive HWB-EH correlations or if environmental injustice is at play. Many interactions among HWB, EH, and demographic factors might plausibly produce the observed correlations. For example, it is unclear if apparent spatial variance in stream health reflects differences in pollution loads, environmental monitoring, regulatory enforcement, political empowerment, or other factors.

Overall, this study highlights the need for future multidisciplinary research to characterize potential toxicological, socioeconomic, and policy linkages between HWB and EH. Examinations of such linkages could inform public investment in environmental programs to enhance cost-effectiveness and equity with respect to HWB outcomes.

The ONB features articles from U.S. Geological Survey Cooperative Fish and Wildlife Research Units across the country. The Units are leading exciting, new fish and wildlife research projects that we believe our readers will appreciate reading about. This story was written by Paul Angermeier, Assistant Unit Leader, Virginia Cooperative Fish and Wildlife Research Unit, a Program in the U.S. Geological Survey Ecosystems Mission Area, at Virginia Tech.

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February 16, 2021