UnEarth Magazine.

Words by Annice Rioux

In September of this year reports were received of around forty pilot whales in distress near a beach in Northumberland. Unfortunately, six individuals later died due to stranding. While this news is devastating to marine mammal lovers, another mass stranding event does not come as a surprise. Andrew Brownlow, the Director of the Scottish Marine Animal Stranding Scheme (SMASS) reported that in the last 10 years, the number of mass stranding events in the UK as well as the number of animals involved in each stranding have increased exponentially. In 2023 and 2024 there were two large-scale events in Scottish waters: the stranding of 55 pilot whales on the Isle of Lewis in July of 2023 followed by that of 77 pilot whales in Orkney in July of 2024. Both of these strandings prompted urgent responses from marine researchers and conservationists, with a focus on possible causes of and solutions to the increase in annual mass strandings in the UK.

While there are many factors that may potentially impact mass strandings, there is no single cause that can explain every event. Pilot whales have some of the highest stranding frequencies, even beyond the UK, mainly due to their strong social bonds within a pod. If one whale is in distress, the rest of the pod will follow, increasing the chance of a mass stranding as they all get pulled closer to the shore. This is thought to be the cause of the mass stranding event on the Isle of Lewis in 2023 as one of the female pilot whales showed signs of a laboured birth, which may have triggered her to strand and the rest of her pod to follow. In other cases human pressures are thought to impact strandings. A prominent human pressure is underwater noise, especially from military sonars and drilling from industrial construction, which interferes with the sonar echolocation of some whales and dolphins. A paper published by researchers at the University of Glasgow in 2025 predicts that these acoustic pressures will continue to increase due to construction of offshore windfarming projects in order for the UK to meet their 2050 energy targets. In addition to noise pollution, humans also exert pressure on marine mammals from fishing and discarded fishing gear called “ghost gear”. Entanglement of large marine mammals, specifically whales, in this ghost gear is an increasing threat, as fishing activity has increased in the North Sea in addition to a rebound in the populations of some whale species following the UK’s ban on whaling in 1986. There are also environmental factors that can impact marine mammals such as soft substrate on sandy beaches. These sediments can impede navigation by disrupting cetacean echolocation, and when combined with onshore winds, can increase the chance of a stranding event.

While many of these factors cannot be influenced by human intervention, many organisations are committed to decreasing human pressures on marine mammals and assisting in rescue attempts during strandings. SMASS is a research and reporting scheme that has published annual reports from 2010 to 2024 outlining the different stranding events that occurred within the year, and reporting necropsy results when available. This data is important to build an understanding of why these stranding events keep occurring. SMASS is also working on expanding public engagement and awareness through outreach programs and volunteering opportunities. The British Divers Marine Life Rescue (BDLMR) is the main organisation that attempts to rescue animals that are still alive when stranded and, when possible, float them back out to sea. One of the only preventative measures that can be taken is to reduce human pressure on marine mammals, specifically dealing with entanglement. Global Ghost Gear Initiative (GGGI) is working across all sectors to solve the problem of discarded fishing gear that puts marine animals at risk.

Beyond the beach, marine mammal mass strandings can affect entire marine food webs by reducing predation pressure on many prey species, such as squid and small bony fish, which impacts aquatic predator-prey relationships and can cause habitat destruction from overgrazing. Whales also play a crucial role in circulating nutrient rich water through the water column, which increases primary production. As the number of live whales decreases due to stranding events, open-ocean food webs are getting fewer nutrients through upwellings of water, which decreases ecosystem productivity. With the number of stranding events continuing to increase, we have to reduce human pressures on marine mammals, and until we can effectively prevent strandings we must fund rescue and response efforts.