dhw's obsession with 'humans plus food'; current studies (Introduction)

by David Turell , Wednesday, December 13, 2023, 16:09 (346 days ago) @ David Turell

Larger forms in species are disappearing, affecting food supply:

https://www.science.org/doi/10.1126/science.adi1826?utm_source=sfmc&utm_medium=emai...

"Current ecosystems are often characterized by an absence of large animals. This downsizing of nature is part of the ongoing biodiversity crisis and involves the loss of larger species as well as the larger individuals within a species, both of which can be linked to historic and ongoing harvesting practices by humans. Such signatures of human activity can be traced back for millennia, which makes it difficult to infer the potential role of larger animals in intact ecosystems. Model simulations suggest that larger animals could have major influences on population dynamics, ecosystem functioning, and resilience to environmental change, and therefore they should be the focus of biodiversity restoration programs. For instance, large predators may impose strong top-down control and prevent destabilizing grazer outbreaks and even promote genetic diversity at lower trophic levels. Large animals could also play a particularly important role in connecting ecosystems.

"Here, we describe the role of large female Atlantic cod (Gadus morhua), which are comparable in body size to those typically reported in archaeological studies of cod bones dating back at least one millennium, in connecting coastal spawning sites. The Atlantic cod is a potentially dominant predator in North Atlantic coastal ecosystems, and individuals can grow to reach a body length well beyond 1 m. However, cod is also a prized catch in fisheries, and many populations have been seriously overfished, in some cases collapsed to a state where recovery is expected to be slow or even unlikely.

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"Our study suggests that the contribution of large female fish to population productivity and stability may go beyond what is already recognized from their high-reproductive-energy output. From a population perspective, a network of spawning sites can indeed act to stabilize overall recruitment of broadcast spawning fish through a connectivity portfolio effect in which some sites are successful in some years, whereas other sites are successful in other years. Similarly, for Atlantic cod, the exact location where the pelagic eggs are spawned will influence in which habitats the juveniles eventually settle for growth and survival. There is evidence for spatial asynchrony in recruitment and juvenile growth of cod occurring on a scale of only a few tens of kilometers, including our study region, suggesting that what stands out as the most favorable spawning site varies temporally.

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"For northern cod found off Newfoundland and Labrador, the egg contribution from older females (≥10 years of age) has declined from an estimated 30 to 40% in the 1960s to a negligible level in more recent postcollapse years. To restore a safe operating space for fisheries, strategies for maintaining the full potential of fish spawning habitat use, set by ecological and evolutionary constraints, should be integrated into management and conservation plans. To that end, a widely supported recommendation for rebuilding size and age structures is to implement slot-size limits in fisheries and fully protected marine reserves connected by seascape movement corridors.

"The mobility expressed by large female cod during the spawning season shows that these fish can play an important role in facilitating connectivity among spawning habitats. Management actions directed toward rebuilding fish life histories could therefore be a meaningful way of improving overall population resilience. Even though the populations of cod in mid- and northern Norway are harvested and far from pristine (59), the continued existence of some very large individuals presents a valuable glimpse of what fully expressed and naturally adapted life histories may add in terms of movement behavior diversity. Unless the genetic basis for such life histories and behaviors has also been eroded by fisheries (48, 60), our finding offers a positive perspective for conservation programs aimed at rebuilding more severely depleted populations and species."

Comment: it is my position after analyzing evolution from the standpoint that God created the process, the goal was to produce large-brained humans with a vast tree/bush of life for their required food supply. How delicate the balance is between a massive human population of over eight billion and growing, is shown by this study. Since evolution has ended in the current situation, it is what God planned and expected, although I assume He hopes we learn to handle the problem properly, not the current case.