2.2.2.1. Enhanced biodiversity and evolutionary potential
The ES (Eecosystem Services) of enhanced biodiversity and evolutionary potential, and enhanced primary production, are interrelated. Via the supporting ecosystem service of nutrient cycling, through abundant releases of iron from whale faeces and nitrogen from urine and faecal plumes, enhanced primary production occurs, including extended phytoplankton blooms (Lavery et al., 2010; Lundsten et al., 2010; Roman and McCarthy, 2010; Roman et al., 2014). In addition to ocean currents meeting and upwelling, the physical movement of animals in the water column, especially larger animals such as whales, contributes to the wider distribution of nutrients and oxygen in the water, leading to greater primary production (James et al., 2017). Areas rich in primary production also tend to be associated with an abundance of prey, and are thus often more biodiverse. In contrast, marine areas which have suffered losses of great whales have been associated with trophic cascades, leading to the associated stock decline of many other species, such as sea otters, kelp forests and birds of prey (Wilmers et al., 2012; Roman et al., 2014). In addition, the sunken carcasses of great whales, of whale falls, provide an important deep-sea habitat for more than 100 species that may be considered whale-fall specialists (Smith et al., 2019). The loss of these habitats as a result of commercial whaling is likely to have had a big impact on the diversity of whale-fall specialists in areas where whales have been hunted for centuries.
2.2.2.2. Climate regulation (carbon sequestration)
Over their lifetime, whales contribute to the removal of carbon from the atmosphere through the accumulation of large amounts of carbon in their bodies (Smith and Baco, 2003; Roman et al., 2014; James et al., 2017). After death, whales sink to the ocean floor. So-called ‘whale falls’ result in the locking in of organic carbon content on the sea floor. Smith and Baco (2003) reported that the carcass of a 40-tonne grey whale can contribute a level of organic carbon content equivalent to around 2000 years of the background flux. In addition, a study by Pershing et al. (2010) reported that restoring baleen whale stocks to pre-whaling levels would remove 1.6 × 105 tons of carbon each year through whale falls.
