Chesapeake Bay Program puts numbers on climate change-related pollution

A man fishes in the Appomattox River, a tributary of the James, in Hopewell in May 2019. Both rivers are part of the Chesapeake Bay watershed. (Sarah Vogelsong/Virginia Mercury)

Chesapeake Bay states will now have specific targets for reducing pollution expected to result from climate change, officials announced Friday morning during a meeting of the Chesapeake Bay Commission. 

The new policy, which is in line with a plan for addressing climate change impacts first set in December 2018, goes beyond the Chesapeake Bay Program’s earlier, more qualitative approach asking states to consider the changing dynamics as part of their cleanup strategies to one that instead quantifies pollution impacts due to climate change for each watershed.

In the last round of cleanup plans formulated by the bay states — a set of documents known as the Phase III Watershed Implementation Plans — only Virginia set a numeric target for pollution reductions linked to climate change. All other states simply offered the required “narrative strategy” for dealing with the issue.

The new approach, said Chesapeake Bay Commission Pennsylvania Director Marel King, was the product of “understanding the influences of climate change were probably going to impact (pollution) loads to the Chesapeake Bay.” 

Among the climate change-related factors likely to affect how much pollution ends up in the Chesapeake Bay are increased rainfall, rising air and ocean temperatures, changes in the area covered by wetlands and increasing salinity, said King. And while some of these global shifts “are actually positive” for bay health and could offset other more negative impacts, she added, ultimately the net result is expected to be millions more pounds of nitrogen flowing into the bay. Excess amounts of this nutrient, which along with phosphorus and sediment is a major focus of cleanup efforts, cause algal blooms in water bodies that block light and cut off oxygen to plants and animals, leading to widespread die-offs. 

The new numeric targets will ask bay states to reduce a total of 5 million additional pounds of nitrogen flowing into the Chesapeake Bay as a result of climate change by 2025. 

For comparison, said Chesapeake Bay Commission Executive Director Ann Swanson, Virginia’s current overall nitrogen reduction goal for 2025 is a little over 4 million pounds, while Maryland needs to cut about 8 million pounds and Pennsylvania more than 30 million. 

Still, the 5 million pound target is significantly less than an earlier estimate by the Chesapeake Bay Program that an extra 9 million pounds of nitrogen reductions would be needed by 2025 to offset the effects of climate change. 

Virginia’s most recent cleanup plan relied on the prior estimate to calculate it would need to reduce state nitrogen loads by 1.7 million pounds. Under the new modeling estimate, said King, “that will drop to about 1.5 million pounds.” 

States will be required to incorporate the new pollution loads in their two-year milestone plans for 2022-2023.