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Loyola biology and environment professor publishes groundbreaking 30-year study on water quality change in the Mississippi River

Loyola press release - April 22, 2016

Decades of research offer insight into wetland plant growth in the Mississippi River Balize Delta.

From 1988 to 2008 David A. White, Loyola University New Orleans Professor in Biological Sciences and the Environment Program, collected data hoping to determine what kind of impact things like temperature and sediment have on wetland biomass.

That’s 30 years of field data collection—an absolutely relentless methodology that offers clear, direct insight into long-term patterns of change in the river. And now Loyola gets to boast about the unique success that his study was, especially since generations of Loyola biology and environment students have participated in the studies.

“Studies conducted over decades of this nature are rare, and the findings could only have come from research of this duration because the high inter-annual (year to year) variability in plant growth hides the observed long-term patterns of change,” White explained.

The study offered not only one of the most—if not the most—direct and comprehensive observations of this change in wetland plant growth, but also a causal explanation for the change.

“To my and my co-author’s knowledge, there are no studies that as clearly show such high correlation of a river's water quality on riverine wetlands that is attributable to human influence,” White said.

He and his co-author, University of Louisiana at Lafayette’s Jenneke M. Visser, published the results of the decades-long endeavor in Aquatic Botany 132 (2016) 5-11 in a study called “Water quality change in the Mississippi River, including a warming river, explains decades of wetland plant biomass change within its Balize delta.”

Key findings of the study included:

  • Wetlands in the Mississippi River’s Balize Delta, USA showed an overall plant biomass increase with a large inter-annual change from 1988–2008.
  • River discharge and sediment negatively impacted the biomass over these decades, whereas river temperature had a positive impact.
  • The decadal plant biomass likely increased because of the impact of a 0.9 °C/decade increase in river temperature on growing season length.
  • The added river temperature increased the growing season 0.7 days each year from 1983–2012, or 14.7 days over the shorter biomass study period.
  • Climate change and land use/cover change in the catchment are likely responsible for the river and wetland biomass change in the Balize Delta.


These findings both inform environmental scientists of the impact of the world’s rivers on their respective wetlands—particularly those with deltas or large flood lands—and the effect humans are having on those wetlands.

“The results show that human impacts within river basins from land use change and climate change—in this case especially warming, but likely changes in discharge and sediment loads, too—are dramatically affecting wetland plant growth,” White explained.

These kinds of studies are groundbreaking and valuable not least of all because the true observation of long-term patterns in nature can offer practical guidance to the state as far as environmental budgeting.

“The increase in plant growth observed in our delta means that more carbon dioxide is removed by photosynthesis, which means less in the atmosphere, which means less global warming,” White explained. “The State of Louisiana's wetland restoration ecologists and planners could see value in the findings when considering monetizing the costs of freshwater diversions and wetland creation. There are significant efforts worldwide to design payments (benefits) for designing projects or changing industry practices and human consumerism to reduce global gas emissions.”

Quite simply, “The more wetlands created in the state, the better,” White said.

White suggests more studies around the world are needed that seek to explain long-term variability in ecosystem properties—whether they’re impacted by humans or not—and is currently working on a second paper from the same research, this one on the long term life cycles of wetlands. A larger body of these studies could offer a better understanding of environmental health on both global and local scales.

“There is no doubt in an ecologist’s mind that there have been, are and will be cascading impacts through the ecosystems, food chains, nutrient cycling from changing river water qualities and thus plant growth,” White said. “Cascading changes in Louisiana wetlands will have subtle impacts on our seafood and recreational industries for those wildlife, fish, shellfish we harvest if we as a society don't react quicker than we are likely to do.”

The reason he believes we are unlikely to react quickly to these problems is that these environmental changes are felt slowly, if at all, by the generations responsible for them. To act to correct our influence on the environment’s health will require a foresight beyond our own or even the next generation.

“The average person in the State will not experience the direct impact of the changes in the river's water quality or plant growth,” White said. “Generationally, the changes will be too slow.”

“We come into the world with our own baselines of knowledge, wanting to say to all the older folks, ‘yeah, yeah, yeah, I know it was different back when you were a kid.’ I had a Loyola undergraduate student several decades ago yell out in class one day, ‘the problem is we don't live (individually) long enough!’ That's all he said. But, he's correct. If each of us would have to wallow in society’s results for an additional 50 to 100 years of life we just might pause a bit longer to straighten up our nest!”

Something to consider as we remember April 22’s Earth Day celebration.