Scientists' warning on endangered food webs

Abstract

Abstract. All organisms are ultimately dependent on a large diversity of consumptive and non-consumptive interactions established with other organisms, forming an intricate web of interdependencies. In 1992, when 1700 concerned scientists issued the first “World Scientists' Warning to Humanity”, our understanding of such interaction networks was still in its infancy. By simultaneously considering the species (nodes) and the links that glue them together into functional communities, the study of modern food webs – or more generally ecological networks – has brought us closer to a predictive community ecology. Scientists have now observed, manipulated, and modelled the assembly and the collapse of food webs under various global change stressors and identified common patterns. Most stressors, such as increasing temperature, biological invasions, biodiversity loss, habitat fragmentation, over-exploitation, have been shown to simplify food webs by concentrating energy flow along fewer pathways, threatening long-term community persistence. More worryingly, it has been shown that communities can abruptly change from highly diverse to simplified stable states with little or no warning. Altogether, evidence shows that apart from the challenge of tackling climate change and hampering the extinction of threatened species, we need urgent action to tackle large-scale biological change and specifically to protect food webs, as we are under the risk of pushing entire ecosystems outside their safe zones. At the same time, we need to gain a better understanding of the global-scale synergies and trade-offs between climate change and biological change. Here we highlight the most pressing challenges for the conservation of natural food webs and recent advances that might help us addressing such challenges.

WITHDRAWN: A global carbon and nitrogen isotope perspective on modern and ancient human diet

“…In part, the observed compression is the result of a general decrease in the trophic level of animal and sh resources extracted for consumption from natural food webs as a result of over-exploitation in recent decades 43 . However, the largest contribution to the apparent decrease in trophic level over the range observed in ancient populations, is likely due to the disconnection of the majority of the modern human population from complex natural food webs and their replacement by the simpler food webs 44 and atter food chains associated with industrial agriculture and farming 45 . This has effectively removed these other sources of trophic diversi cation from the human diet.…”

“…Comparison of the ancient and modern isotope results presented here suggest that modern human food webs have become dramatically compressed as a result of the ongoing expansion of industrial agriculture and pastoralism at the expense of natural ecosystems. In turn, this is resulting in a cascade of 'rewiring' to remaining natural terrestrial and marine food webs globally 60 that can reduce complexity, and therefore the resilience, of global ecosystems in the face of accelerating environmental change [43][44][45]61 .…”

A global carbon and nitrogen isotope perspective on modern and ancient human diet

“…In part, the observed compression is the result of a general decrease in the trophic level of animal and fish resources extracted for consumption from natural food webs as a result of overexploitation in recent decades (47). However, the largest contribution to the apparent decrease in trophic level over the range observed in PHB populations is likely due to the disconnection of the majority of the modern human population from complex natural food webs and their replacement by the simpler food webs (48) and flatter food chains associated with industrial agriculture and pastoralism (49). This has effectively removed these other sources of trophic diversification from the human diet.…”

“…Comparison of the PHB, modern subsistence, and modern urbanized isotope results presented here suggest that modern human food webs have become dramatically compressed as a result of the ongoing expansion of industrial agriculture and pastoralism at the expense of natural ecosystems. In turn, this is resulting in a cascade of "rewiring" to remaining natural terrestrial and marine food webs globally (65) that can reduce the complexity, and therefore the resilience, of global ecosystems in the face of accelerating environmental change (47)(48)(49)66).…”

Adjusting GDP for ecological deficit: the Index of Debt to the Future (IDF)

“…This paper has been strongly motivated, as many others, by an increasing wave of literature showcasing that humanity's current trajectory is unsustainable. This literature includes the conversations on climate change (IPCC 2018; Ripple et al 2019), on the need to sustainably provide healthy food for an increasing population through 2050 and beyond (Clark et al 2019;Heleno, Ripple, and Traveset 2020;Springmann et al 2016;Willett et al 2019), on the collapse of biodiversity (Ceballos, Ehrlich, and Dirzo 2017; Crist, Mora, and Engelman 2017; Dasgupta 2020), to name but a few areas. Although many studies, including the Scientists' Warning Series, aim to convey an urgency of action, the timeframe of policy documents and international organisations is usually from 2030 at the earliest to 2050, even to 2100.…”