Effects of global warming on marine mammals
The effect of global warming on marine mammals is a growing concern. Many of the effects of global warming are currently unknown due to unpredictability, but many are becoming increasingly evident today. Some effects are very direct such as loss of habitat, temperature stress, and exposure to severe weather. Other effects are more indirect, such as changes in host pathogen associations, changes in body condition because of predator–prey interaction, changed in exposure to toxins, and increased human interactions. Marine mammals that have been affected by climate change include walruses, seals, and polar bears.
During the last century, the global average land and sea surface temperature has increased due to an increased greenhouse effect from human activities. Warming has even reached depths of more than 700 meters (30% of ocean warming over the past decade has occurred in the deeper oceans below 700 meters). Many marine mammal species require specific temperature ranges to survive. Ocean warming will therefore lead to increased species migration, as endangered species look for a more suitable habitat. If a species cannot successfully migrate to a suitable environment, unless it learns to adapt to rising ocean temperatures, it will face extinction. Sea level rise is also important when assessing the impacts of global warming on marine mammals, since it affects coastal environments that marine mammals species rely.
Changes in temperatures change the location of areas with high primary productivity. Primary producers, such as plankton, are the main food source for marine mammals such as some whales. Species migration will therefore be directly affected by locations of high primary productivity. Water temperature changes also affect ocean turbulence, which has a major impact on the dispersion of plankton and other primary producers. Due to global warming and increased glacier melt, Thermohaline circulation patterns may be altered by increasing amounts of freshwater released into oceans and, therefore, changing ocean salinity. Thermohaline circulation is responsible for bringing up cold, nutrient-rich water from the depths of the ocean, a process known as upwelling.
Polar bears are one of the marine mammals that are most at risk due to climate change. The biggest issue for polar bears related to climate change is the melting of ice as a result of increasing temperatures. When the ice melts, polar bears lose their habitat and food sources. Although polar bears have been known to eat more than 80 species of animals, most of their diet consists of seals, which are also endangered by global warming. There have been an increasing number of polar bear drownings because they become exhausted by having to swim farther to find ice or prey.
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