Here is a list of the main threats that face cetaceans in the marine environment.
Plastic pollution has become a major conservation issue over the last decade and is a growing problem. Plastics enter the sea through being dumped, blown from land, industrial outfalls and discarded from coastal communities. It harms marine life through entanglement or ingestion and destroys habitats by smothering the seabed and disturbing benthic communities. The problem is now so large that 'rubbish gyres'have formed on the oceans surface in the Pacific ocean.
The ingestion of marine plastics is now well documented in many species from birds to turtles, seals and whales. Bottle caps, plastic straws, plastic bags and plastic sheeting are regularly found ingested by these animals. Most recently a Cuviers beaked whale was found dead in Norway with 30 plastic bags in its stomach. Microplastics (plastic particles smaller than 5mm) are also a problem for filter-feeding marine invertebrates. Microplastics are mainly found in cleaning products and cosmetics as well as from the incomplete breakdown of larger plastic debris. These pieces of plastic take decades to break down and affect the base of the foodchain for many marine ecosystems. As these animals cannot break the plastics down, the amount of microplastics ingested increases exponentially as it moves up the foodchain.
The incidental capture (or by-catch) of whales, dolphins and porpoises in fishing gear is one of the greatest threats to cetaceans, particularly the harbour porpoise. Gill nets, crab/lobster pots and traps are amongst the most impactful - the net fibres have a high tensile strength and are very thin in diameter so are almost invisible in water but are easily able to cut through skin. This type of gear is also made out of a very durable plastic which does not rot and therefore has a long life slowly breaking down into microplastics.
It is estimated that around 640,000 tonnes of new ghost fishing gear is lost or discarded in our oceans every year across the world. That's equivalent to more than the weight of 12 titanics!
Collisions between cetaceans and vessels are a significant cause of death, particularly for the larger whales. With an increase in the volume of traffic, growing ship size and increasing speed set to occur on our seas over the coming decades this problem is expected to become more and more prevalent. Currently research is being conducted by various groups, identifyting what can be done to prevent ship strikes from occurring.
ORCA ran an innovative pilot study in 2017 to investigate the prevalence of ship strikes and near misses with fin whales in the Bay of Biscay. This was extended into 2018 and is continuing in 2019, hopefully resulting in important findings to inform policy and ships crews.
It is believed humans have been engaged in whaling since prehistoric times. In 1986 the International Whaling Commission (IWC) banned commercial whaling. However, since then over 50,000 whales have been killed because of loopholes in the ban that allows some countries to continue this barbaric tradition. Today Norway, Iceland, the Faroes and Japan still hunt whales, and, based on recent figures, these countries will kill around 2,000 whales this year, including fin whales, minke whales, Bryde's whales, humpback whales and sperm whales.
The whaling industry is in decline and the demand for meat is falling, but ORCA believe that opposition to this cruel trade must be maintained by the public, NGO's and governments so that those countries defying the global consensus will eventually be forced to end commercial whaling.
Changes in temperature, freshening of seawater, acidification, sea level rise, loss of icy habitats and the decline of food sources are just some of the threats posed by climate change. The current topic in regards to climate change is that of ocean acidification. Ocean acidification is when CO2 dissolves into seawater, making it more acidic. The increase in acidity dissolves calcium carbonate, a critical compenent of various marine ecosystems. Over the last century, the amount of CO2 in the atmosphere has almost doubled, and due to the larger surface area of the ocean in comparison to land, it absorbs a greater proportion of this CO2. Unfortunately, many marine organisms use calcium carbonate as the basis for their skeleton (e.g. corals, plankton, gastropods and bivalves), and so will be adversely affected by the increase in acid in the ocean.
Baleen whale populations will be directly affected by ocean acidification, as they eat plankton and krill, which have a calcium carbonate skeletal base. It is projected that plankton populations will decrease by as much as 40% by 2050, reducing the baleen whales food by half. It is also theorised that increased acidity would allow sounds to travel up to 70% further underwater, increasing the amount of background noise in the oceans which could significantly affect the behaviour of some marine mammals (Hester et al; 2008).
K. C. Hester, E. T. Peltzer, W. J. Kirkwood, and P. G. Brewer, Unanticipated consequences of ocean acidification: A noisier ocean at lower pH. 2008. Geophysical Research Letters, Vol. 35 #31 (October 1, 2008)