A new study on ageing in the animal kingdom has highlighted how urgently Earth's oldest and wises creatures must be protected, with knowledge and environmental stability lost due to human intervention.
The research team - led by Charles Darwin University (CDU) and including the University of Exeter - explored the consequences of the loss of old, often large and wise animals in the wild and the value these individuals have to scientific knowledge, biodiversity and more.
Humans are responsible for the decline of these animals. The review explains how in freshwater and ocean environments, the oldest age-classes of fish have been depleted, and extremely old corals are being harvested and are irreplaceable within human lifespans.
On land, poaching, trophy hunting, predator hunting and recreational harvests are responsible for the loss of other types of old animals. On land and sea, old animal decline is also caused by habitat loss, disease and extreme climate events.
Lead author Dr R. Keller Kopf, an ecologist and senior lecturer in CDU's Research Institute for the Environment and Livelihoods, said older animals offer unique biological functions and ecological knowledge, and provide important services humans rely on.
"In addition to their intrinsic biodiversity value and slower rate of recovery in response to human activities, the loss of old animals ultimately threatens the long-term sustainability and stability of ecosystems on which humans depend," Dr Kopf said.
"They are especially important for ecosystem services such as fisheries whereby old individuals appear to provide the stability to populations, yet they are selectively harvested."
Professor Lauren Brent, from the University of Exeter, said: "Our research shows that old animals can be beneficial in a variety of ways.
"We are losing them at an alarming rate. We need more research to understand the contribution they make to their societies, and we need to step up efforts to protect them."
Dr Kopf added: "Old individuals of long-lived species such as elephants, whales and humans accumulate knowledge over long time-periods, and - among many other benefits - this allows them to provide better care of their offspring or grand-offspring.
"In some of these species, especially humans, grandmothers increase the probability of grand offspring surviving and going on to reproduce.
"In fish and other cold-blooded animals, older individuals generally continue to grow throughout life, and this allows them to increase the number of offspring they produce."
Dr Kopf said management strategies and policies would need a long-term approach, into years and decades, for the successful conservation of these animals.
"A new method of conservation management and policy is required, which we refer to as 'longevity conservation'," Dr Kopf said.
"The International Union for the Conservation of Nature Red List, and United Nations Convention on Biological Diversity must begin to recognize 'longevity depletion' a global threat to biodiversity and the sustainability of life on Earth.
"Fisheries management agencies should develop policy and assessment approaches to recognise and prevent 'longevity overfishing' - it is currently not recognised as a type of overfishing but is a likely cause of fisheries collapse and increasing volatility."
The study was conducted with an interdisciplinary team of researchers from CDU, the University of Exeter, Charles Sturt University, Macquarie University, the Amboseli Trust for Elephants in Kenya, the University of Stirling and Texas A&M University.
