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Proposed Dredging Changes

One of the largest threats currently facing Georgia’s sea turtles is the U.S. Army Corps of Engineers. They want to alter their dredging schedule from winter to summer months; doing so during this time would harm many of Georgia’s ‘summer’ marine species — especially nesting sea turtles.

Why Dredging Occurs

Dredging occurs every year to ensure that Georgia’s harbors and channels are safe and navigable for commercial shipping. Dredging removes sediment from the ocean floor, deepening the channel for ships carrying automotives and other roll-on/roll-off cargo. The type of dredging used in these instances requires a ‘hopper dredge’: it operates much like a giant vacuum cleaner, sucking sediment off the bottom of the ocean and pulling it through rotating blades. Most sea turtles do not make it through intact.Routine Operations and Management Dredging has historically taken place during a strict winter window (December 15 – March 31) for more than 30 years. This strict window was established after a series of sea turtle fatalities in the 1990s, when the National Marine Fisheries Service determined dredging posed a severe threat to the existence of loggerhead sea turtles.

What's Different

The Army Corps’ move to change the dredging schedule is in response to the 2020 SARBO (South Atlantic Regional Biological Opinion), a document that contains over 600 pages of biological assessment for dredging activities in the Southeast United States. It is an update from the 1997 version.Using this document, the Army Corps claims that changing the dredging window would significantly reduce risks to multiple species under the Endangered Species Act, while only slightly increasing risk to loggerhead sea turtles. They further argue that shifting the dredging schedule from winter to summer would actually protect North Atlantic right whales, a species that calves in Georgia waters during winter.  According to Georgia DNR’s scientific analysis, spring and summer dredging could conceivably kill as many as 87% of the females nesting in the vicinity of the Brunswick shipping channel, and 47% of those near the Savannah shipping channel. Georgia’s marine biologists strongly object to this change.

Would a Change Help Right Whales?

Local marine experts say they were not consulted by the Army Corps about the proposed change, and that there is little evidence that right whales are affected by dredging. Right whales and their calves (who weigh approximately 1 short ton) cannot fit into, or be sucked into, a dredge the way sea turtles can. Right whales seldom come into the shallow channels where dredges are located, suggesting that when protective measures are in place (like reducing dredge ship speeds), strike likelihood remains low. In the 2020 SARBO, it shows that right whales are minimally impacted by dredging. The document states that interactions, like ship strikes, between right whales and dredging related vessels is very low — citing only 2 reported dredge vessel strikes on North Atlantic and South Atlantic (closely related) right whales, despite decades of dredging worldwide. In the NMSF (National Marine Fisheries Service) 2011 Environmental Assessment document

Issuance of a Science Research Permit for Research on North Atlantic Right Whales in the Southeast United States dredging effects on right whales are categorized under habitat degradation.  The primary anthropogenic threat facing endangered North Atlantic right whales is entanglement in the heavy fishing gear used by lobster and snow crab industries in New England. An article in Frontiers in Marine Science, Future Directions in Eubalaena spp.: Comparative Research to Inform Conservation, states that from 2010 to 2015, 85% of diagnosed right whale mortalities were due to entanglements and 15% were due to ship strikes. Individual reproductive female right whales are the most important in the population, and data supports that a loss of just 4-6 females a year will lead the population to extinction. 

Scientists also see a relationship between poor right whale breeding success and low zooplankton populations, which are their main food source. Their feeding grounds in South Georgia have been affected by increasing ocean temperatures. The combined stress of entanglement, ship strikes, and feeding changes required by climate change make it difficult for the female right whales to put on enough weight to calve successfully. The fate of the right whale remains precarious; those that work along the coast understand this and are deeply invested in the recovery of the North Atlantic right whale. Georgia DNR invests heavily in teams that help with detangling right whales trapped in fishing gear. If endangered right whales could be helped by switching the dredging window, there would be no argument about the schedule change from marine experts. However, there is little evidence that right whales would benefit from this change — but there is 50 years of data showing that endangered sea turtle populations would be negatively impacted by dredging during their nesting season. This “save the whale” spin is a way for the Army Corps of Engineers to appear environmentally-conscious while still getting the cost-savings and convenience they so desperately want.

An article about changing the dredging window for North Carolina’s ports, published in September 2020 in CoastalReview.org, Corps Asks State to Eliminate Dredge Window, notes that the hopper dredges are in short supply — with only 13 available to operate on the coast from Maine to Florida and across the Gulf Coast to Texas — and that eliminating the hopper dredging window would save the Army Corps millions of dollars.

If you need more proof, an Army Corps dredging document from August 1996, Savannah Harbor Long Term Management Strategy (Appendix A), states that environmental windows and other restrictions limit dredging operations to ensure that environmental resources receive appropriate protection. Those limitations often increase the cost of dredging…if the restrictions were lifted or reduced, lower dredging costs would result.”

The window that excludes hopper dredging from December 1 to April 1 to protect sea turtles is one of the restrictions that (unfavorably) impacts dredging costs.

Why It's So Important

Since the 1970s, biologists have been collecting data to help pinpoint the best strategies to protect Georgia’s sea turtles. One major takeaway is how critical adult sea turtles are for the overall species survival: population models show that if a large number of hatchling and juvenile sea turtles are killed, the population likely will be able to recover.  But if adult sea turtles are lost, there would be a significant setback to the population.Sea turtles don’t reach sexual maturity until they are 30 years old, and it is estimated that it takes a minimum of 36 years for a female sea turtle to replace herself in the population. Due to low hatchling survival odds, it could take a sexually mature female anywhere from 6 to 20 years of egg-laying before she has likely produced enough offspring to replace herself in the population.  For each extra decade she lives, up to around 70 years old, she will be adding sea turtles to the population.This is why removing nesting adult turtles sets recovery back by decades. In an article by the Savannah Morning News, Georgia wildlife biologist Mark Dodd said that dredges killed six loggerhead turtles in Brunswick and Savannah after 15 days of dredging in a Sep. 2009 trial run of dredging outside Georgia’s seasonal windows. The trial was quickly stopped due to the high impact dredging had on sea turtles outside of the protective window.

What you can do

Stay tuned for additional developments on this issue.