Report: Feeling the Heat: Whales and Climate Change
- Impacts of climate change in the Polar Regions
- What is happening to the krill?
- How are krill populations affecting the whales?
- The conservation effort
Download a printable version of the ‘Feeling the Heat: Whales and Climate Change’ report.
There has been increasing evidence that the Earth is getting warmer and that human activities are the main cause. The increase in greenhouse gases, such as carbon dioxide and methane, and the correlating rise in global temperatures are causing sea levels to rise as a result of thermal expansion of the oceans and melting of ice. The best estimates, from the Intergovernmental Panel on Climate Change, predict global temperatures to increase by one to three degrees Celsius, and sea levels to rise anywhere from 15 to 95 centimetres by 2100 (Baker, J 1999). Although there has been some progress in ratifying agreements to curb the rise in global temperature it is still dubious as to their success.
The Kyoto protocol which came into force on the 16th February 2005 has still yet to make one of the biggest polluters namely the US to sign up to the agreement. The protocol’s original target was to reduce emissions by 5.2% below 1990 levels but with the absence of US support and other factors the original target had to be reduced to just 2%. Another growing concern is that of the developing countries growing contributions to global emissions resulting in ever more rising temperatures. With emissions from developing countries expected to more then double between 2002 and 2030 and global carbon dioxide to reach a 50% increase, a stronger worldwide commitment to reducing greenhouse gas (GHG) emissions is required. In terms of the impact on cetaceans, changes in climate can either directly impact them by altering their habitat, changing reproductive rates and altering migration routes and geographic ranges or indirectly, where the shifts in climate can change the abundance, distribution and composition of cetacean prey species.
Impacts of climate change in the Polar Regions
In 2005, the International Climate Change Task Force revealed fears of catastrophic global events such as the melting of the Greenland, which has doubled since 1990, the break up and melting of the Antarctic ice sheets. There is also fear of the shut down of the thermohaline ocean circulation, which is instrumental in the regulation of sea temperatures and therefore the marine ecosystems. This system cycles water from the surface to the ocean floor. It is also responsible for the uptake of vast amounts of carbon dioxide which if left in the atmosphere would further warm the earth.
With the looming prospect of these changes happening within the next few decades scientists have developed models with high statistical confidence to show the link between human activities and warming of the worlds oceans to remove any doubt of our contribution and therefore our responsibility to try and lessen the potential impacts. The effects of climate change has been linked with changes in migratory patterns, destruction of habitat (particularly in nutrient-rich polar seas), and drastic changes in ocean circulation, vertical mixing and overall climate patterns. These changes in nutrient availability and biological productivity, adversely affect the structure of marine ecosystems from the bottom of the food chain to the top.
In 2004, the Arctic Climate Impact Assessment (ACIA) was published by more then 250 scientists and members of Arctic indigenous organisations over a period of four years. It concluded that temperatures in the Arctic are to rise two to three times faster then the global average as a result of increased emissions. Average annual sea ice has decreased by 8%, nearly one million square kilometres in thirty years. Several climate models have predicted an ice free summer in the Arctic by the end of the century (Smith, 1999. ibid).
The warming trend documented for the Antarctic Peninsula since the 1940s has already affected the frequency of extensive sea-ice cover in the Southern Ocean. Cold winters with extensive sea-ice cover occurred on average in four out of five in the middle of the last century, but have decreased to just one or two years in five since the mid-1970s. One function of this trend appears to be a decline in the abundance of krill in the Southern Ocean by as much as 80% since the 1970s.
Another factor to climate change is ozone depletion. In 1985 the ozone hole was discovered over the Antarctic. The size of the ozone hole has been increasing and it reached a record size of 28.4 million km2, which is three times the size of the US, which was detected by NASA in 2000. It has also been documented that a depletion in ozone over the Arctic, Europe and North America has been up to 60% in some areas. Chlorine is the worst ozone depleting chemical which is derived from chlorofluorocarbons (CFC). One single molecule of CFC can destroy 100,000 molecules of ozone. Ozone is the molecule that protects us from the UV radiation from the sun, without it skin damage, prey depletion, and ecosystem alteration can occur. For example studies in the Antarctic on the effects of UV on the polar marine life showed that under ozone hole conditions the primary productivity rate dropped by 6-23% as a result of elevated UV radiation
What is happening to the krill?
Sea ice is the engine that drives Antarctic ecosystems with many of the key species depending on availability of winter ice. The ice pack is forming later and retreating earlier resulting in serious impacts on the abundance of krill, the backbone of the Antarctic food chain. The most important species in most sectors of the Antarctica is krill says William Fraser, a principle investigator for the palmer Long Term Ecological Research program (LTER).
The Norwegian word for whale food, krill, aggregates in super-swarms that can reach a density of 30,000 individuals per square meter, attracting whales, which can eat three tons of krill in a single feeding, and fisheries, which net an average 100,000 metric tons per year. Production in the Antarctic is especially high along the sea ice edge because the ice is thinner allowing more light to penetrate and when the process of ocean mixing causes an up-welling of nutrient-rich deep water. When the ice forms too late the production lessens impacting on zooplankton populations like krill that graze under the ice surface on ice algae. ”The ice edge is an absolutely critical habitat, a nursery for larval krill.” says Scott Gallager, a marine biologist at Woods Hole Oceanographic Institution (Woods Hole, Massachusetts, United States).
However there is growing evidence that global climate change has led to a reduction of ice algae, the main food source of krill. In addition, the hole in the ozone layer increases the amount of UV radiation reaching the Earth’s surface, and may reduce the algae’s productivity. Scientists have found that UV can kill the phytoplankton and therefore significantly affecting the number of krill. On the other hand some of the phytoplankton have shown adaptive qualities to increasing UV by developing UV-absorbing amino acids, this however makes them less edible for the krill.
How are krill populations affecting the whales?
A recent observational study of 1,800 right whales in the southern Atlantic has shown that climate change is linked to the decrease in the whales’reproductive success (Bakalar. N, 2006). The experts believe the problem has arisen indirectly through the decrease in their food supply, mainly krill. Since 1971 the scientists have been observing a population of Southern right whales that gather off Argentina’s Peninsula every year between June and December. This group according to the International Whaling Commission has a healthy population of 8000 and growing. A female right whale needs three years between births. However, if a calf aborts or dies, a female needs two years to recover, and the interval expands to five years. The study has found a relatively large number of five-year calving intervals, that suggests there is a problem with calve survival and not that females aren’t able to get pregnant. It has been hypothesised that the reduced availability of krill has caused mothers to abort or calves to die. A three year study from 1983 to the year 2000 charted and compared sea surface temperatures in the Southwest Atlantic with the breeding success of the right whales off the coast of Argentina. A strong correlation was found between the number of right whale calves born and changes in sea-surface temperature in the autumn of the proceeding year (taking into account the appropriate time lags). The results were clear: as water temperature rise from the norm, calf output declines. Even small changes in sea surface temperatures circumpolar to the Antarctic could affect southern whale population dynamics.
It is believed that krill constitutes a large portion of the whale’s diet but as yet there is insufficient evidence to show a direct link between drop in numbers of this prey and the reproductive success of the whales. Krill is believed to be a key factor in the reproductive success rate of the whales but a deep understanding of their role and affect on predator populations when climate temperatures rise has yet to be understood. The researchers strongly suspect an inverse relationship between krill density and sea surface temperature. In other words the warmer the water gets, the less krill there are.
The conservation effort
In 1993, the IWC specifically directed its Scientific Committee to ”give priority to the effects of environmental change on cetaceans in order to provide the best scientific advice for the Commission to determine appropriate response strategies to the new challenges’’. The following year, the Scientific Committee concluded that ”environmental threats affect all species of cetaceans, [and that] the IWC may have to contemplate response strategies outside the direct management of whaling operations if it wishes any identified threats to be alleviated.” However, lack of funding into this area is limiting their conservation effort.
Campaign Whale is concerned at the potentially disastrous impact of global environmental change on whales and dolphins, and other sea life. This concern is exacerbated by worries that the IWC’s new management plan for renewed commercial whaling, the Revised Management Procedure (RMP), does not take environmental threats to whales into account adequately. Only two sets of data (population estimates and historical catches) are entered into the RMP. No other data, such as the changing state of the ecosystem or details about population dynamics (e.g. sex or health of the animals), are considered. This means that the impacts of environmental change, which are not immediately lethal but lead to a decrease in reproduction rates, will not be factored in until all removals from the population exceeded replacement and a population decline was identified. Even then, all the RMP would do is to reduce the quota set on the declining population. It could not do anything to mitigate the impact of the environmental threat(s) responsible for that decline.
The increasing threat from environmental changes demands that greater attention is given to the work and direction of the Scientific Committee, in order to re-direct its focus away from merely counting whales and calculating catch quotas, to work that will evaluate and address the conservation status and threats to whales. Delaying any reopening of whaling while this evaluation is undertaken is good precautionary science and is in line with fundamentally accepted environmental principles. Only last year, the G8 Environment Ministers released the following communique: ”We wish to express our grave concern at the continuing threat to the oceans and seas and their biological diversity posed by marine pollution, changes in coastal structure, unsustainable fishing practices and other threats. We undertake to make renewed and co-ordinated efforts to counteract these dangers and to promote sustainable use and preservation of the biological diversity of the seas by means of measures at national, regional and global level.”
Campaign Whale believes the IWC’s Scientific Committee should reprioritise its work away from the exploitation of cetaceans and begin a comprehensive assessment of the environmental threats to whales, and an urgent programme of remedial action.
- Bakalar, N for National Geographic News, January 18, 2006
- Baker, J 1999 NOAA News Online (Story 192)
- As the Antarctic Ice Pack Recedes, a Fragile Ecosystem Hangs in the Balance Liza Gross
- PLoS Biology Vol. 3, No. 4, e127 DOI: 10.1371/journal.pbio.0030127
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