Right Whale Extinction Predicted by 2050
Author: Birgitt Keinanen, Edited by: Dr. Priya Roy
Current situation of the North Atlantic Right Whale in the Gulf of Maine
Figure 1: The Majestic North Atlantic Right Whale. Photo Credit: Brian J Skerry, National Geographic
In 1970, the North Atlantic Right Whales (Eubalaena glacialis) were listed as endangered under the Endangered Species Act. Since then, the North Atlantic Right Whale population has continued to decline. There are an estimated 400 North Atlantic Right Whales remaining, with fewer than 100 breeding females. In 2017 at least 17 whales died, and in 2018 no calves were born [1]. Only 12 births have been observed in the three calving seasons since 2017. With deaths outpacing the births in this population, the alarming downward trend forecasts that North Atlantic Right Whales may become extinct within 30 years [2] (see Figure 2).
Figure 2. Number of calves born (light blue) compared to known reproductive females available to calve (dark blue). The orange line is the percentage of females available to calve that gave birth from 2009 to 2019. Data from the 2019 NARWC Report Card.
Read more about their current status here
The National Oceanic and Atmospheric Administration monitors the Northeast Shelf Ecosystem of the North Atlantic Ocean, part of which includes the Gulf of Maine. This is important because the Gulf of Maine has been found to be one of the world’s fastest warming ocean ecosystems. The data collected includes (but is not limited to) both sea surface and bottom temperatures of the water column. Starting in 2008, the bottom temperature did not drop below 8.5 °C and continued to increase in temperature for the next seven years. The bottom temperatures still have not returned to the mean temperature of 7.9°C. The data collected shows a significant trend in the warming of the bottom (see Figure 3). Research has shown that as early as 2008 the North American Right Whales have shifted their traditional foraging routes farther out to sea as a result of this warming [1].
Figure 3. Bottom temperatures for the second half of 2018 in the Gulf of Maine (Source: noaa.gov). These time series plots contain the linear trend shown in red with an indication of the significance of the trend in the title and a change point indicator shown in blue.
Read more on warming of the Northwest Atlantic Ocean here.
Why is this happening?
The North Atlantic Right Whale feeds on tiny ocean creatures called copepods which are only a couple of millimeters long (Calanus finmarchicu) (see Figure 4). Scientists estimate that each whale needs to eat 2,000 pounds of this lipid-rich organism a day. The trouble is that the life-cycle of these invertebrates requires a dormancy period (or diapause) in cold water during the summer months [3]. This usually occurs 100 meters below the ocean’s surface in the Gulf of Maine. But due to the warming temperatures of the bottom of the gulf, the copepod’s habitat has shifted farther out to sea. Along with their shift, the foraging locations of the whales has relocated. This new location puts North Atlantic Right Whales in waters where they are not protected from collisions with ships or entanglement in fishing gear when they surface to breathe [4].
Figure 4. Copepod (Calanus finmarchicu)
Credits: https://www.sintef.no/globalassets/project/calanus/graphics/calanus.jpg
Read more about the cool Copepods here
The shift in both species is due to the warming of what is called the Atlantic Meridional Overturning Circulation (AMOC).
How does the AMOC work?
The Atlantic Meridional Overturning Circulation (AMOC) (see Figure 5) consists of ocean currents that work as a system driven by differences in temperature and salt content. As tropical warm water flows north, it cools, and evaporation occurs, increasing salinity. When the temperature of the water cools and the salt content increases the water becomes denser. This causes it to sink deep into the water column. The colder, denser water then spreads southwards below the warmer surface layer. Eventually, it returns to the top and warms. This process is called “upwelling” and completes the circulation [5]. In the case of the Gulf of Maine, the deeper waters in the AMOC are remaining warm and are responsible for the shift in location of copepod abundance [6].
Figure 5. Atlantic Meridional Overturning Circulation (AMOC) credit: R. Curry, Woods Hole Oceanographic Institution
Learn more about the Woods Hole Oceanographic Institution here
What does the Future Hold?
The low calf production of the North Atlantic Right Whales in 2018 is a sign that they have not found sufficient supply of forage in their new feeding grounds [7]. Some models suggest that a healthy whale population can rebound after finding and adapting to a new habitat [8]. However, as the world’s oceans are warming, the Gulf of Maine is likely to see higher temperatures in the future and the North Atlantic Right Whale population is already struggling. If they have to spend more time looking for food this will lead to additional mortality and decreased births. Under the Endangered Species Act, the National Oceanic and Atmospheric Administration is required to have a plan of conservation and recovery (NOAA Right Whale Protection Plan). The major actions in the plan includes the reduction of injury and mortality caused by the fishing industry and vessel collisions. Implementing protection strategies in the whale’s new feeding ground will be an important aid to their recovery. With the change in the water temperatures of the Gulf of Maine these feeding areas may shift again, which means continuous monitoring is necessary.
Read more about conservation efforts in these whales here.
References:
Corkeron, P., Hamilton, P., Bannister, J., Best, P., Charlton, C., Groch, K. R., ... & Pace III, R. M. (2018). The recovery of North Atlantic right whales, Eubalaena glacialis, has been constrained by human-caused mortality. Royal Society open science, 5(11), 180892.
Daoust, P. Y. (2017). Incident Report: North Atlantic right whale mortality event in the Gulf of St. Lawrence, 2017. Fisheries and Oceans Canada.
Mayo, C. A., & Marx, M. K. (1990). Surface foraging behaviour of the North Atlantic right whale, Eubalaena glacialis, and associated zooplankton characteristics. Canadian Journal of Zoology, 68(10), 2214-2220.
Rolland, R. M., Schick, R. S., Pettis, H. M., Knowlton, A. R., Hamilton, P. K., Clark, J. S., & Kraus, S. D. (2016). Health of North Atlantic right whales Eubalaena glacialis over three decades: from individual health to demographic and population health trends. Marine Ecology Progress Series, 542, 265-282.
Saba, V. S., Griffies, S. M., Anderson, W. G., Winton, M., Alexander, M. A., Delworth, T. L., ... & Zhang, R. (2016). Enhanced warming of the N orthwest A tlantic O cean under climate change. Journal of Geophysical Research: Oceans, 121(1), 118-132.
Sherwood, O. A., Lehmann, M. F., Schubert, C. J., Scott, D. B., & McCarthy, M. D. (2011). Nutrient regime shift in the western North Atlantic indicated by compound-specific δ15N of deep-sea gorgonian corals. Proceedings of the National Academy of Sciences, 108(3), 1011-1015
Stokstad, E. (2017). Surge in right whale deaths raises alarms.
Tulloch, V. J., Plagányi, É. E., Brown, C., Richardson, A. J., & Matear, R. (2019). Future recovery of baleen whales is imperiled by climate change. Global change biology, 25(4), 1263-1281