Periodic Reporting for period 4 - DEADSEA_ECO (Modelling Anthropocene Trophic Cascades of the Judean Desert Ecosystem: A Hidden Dimension in the History of Human-Environment Interactions)
Période du rapport: 2023-07-01 au 2023-12-31
The DEADSEA_ECO project investigates the impact of humans on wild mammal communities in antiquity, focusing on large predator hunting. We sought evidence of humans' ability to cause a top-down trophic cascade effect, where hunting top predators triggers a large-scale reorganization of the food web in a study region. Understanding trophic cascades' potential effects on modern ecosystems is crucial, and finding evidence in the archaeological record could significantly enhance our comprehension of human impact on pre-modern ecosystems.
The DEADSEA_ECO project holds societal relevance. Top-down control by carnivores on herbivore populations is integral to newer nature conservation and restoration approaches, such as trophic rewilding. These methods often face criticism due to their reliance on a limited number of scientific studies examining the effects of installing or removing top-down control in an ecosystem. Additionally, existing case studies lack chronological depth, monitoring effects observable over a few decades at most. To gain a firmer grasp of centennial or millenial trophic cascading effects, we need to develop and test a methodology for detecting top-down cascading effects on a longer time scale. The DEADSEA_ECO project was specifically designed for this purpose. It stands out for demonstrating the interaction between humans, carnivores, and herbivores over millennial time-scales.
The project's primary objectives were to model the effects of human settlement intensification and top-predator hunting on a top predator and its major prey populations. Our study region was in the southern part of the Judean Desert, Israel, where we applied advanced survey and dating methods to settlements, stone-built hunting traps, and fossil-bearing cave deposits.
The DEADSEA_ECO project holds societal relevance. Top-down control by carnivores on herbivore populations is integral to newer nature conservation and restoration approaches, such as trophic rewilding. These methods often face criticism due to their reliance on a limited number of scientific studies examining the effects of installing or removing top-down control in an ecosystem. Additionally, existing case studies lack chronological depth, monitoring effects observable over a few decades at most. To gain a firmer grasp of centennial or millenial trophic cascading effects, we need to develop and test a methodology for detecting top-down cascading effects on a longer time scale. The DEADSEA_ECO project was specifically designed for this purpose. It stands out for demonstrating the interaction between humans, carnivores, and herbivores over millennial time-scales.
The project's primary objectives were to model the effects of human settlement intensification and top-predator hunting on a top predator and its major prey populations. Our study region was in the southern part of the Judean Desert, Israel, where we applied advanced survey and dating methods to settlements, stone-built hunting traps, and fossil-bearing cave deposits.
Our archaeological integration of previous archaeological work in the study region with our own high-resolution surveys and excavations has yielded a detailed record of human settlement intensity in the study region. The team has also surveyed all the known leopard traps in the region, and dated the age of their construction using a method known as Optically Stimulated Luminiscence. These two major efforts enabled us to quantify the peaks and troughs of human activity in the southern Judean Desert. Our results attest a quick growth of the major settlement in the Ein Gedi Oasis during the 8th century BC. With some shifts in size and location of the settlement core, the major settlement lasted until the 6th century AD, after which a long period of abandonment followed, punctuated by a short-lived, small village that emerged in the oasis during the Middle Ages. Surprisingly, this period of settlement abatement also witnessed a peak in leopard trap construction, suggesting that top-predator hunting was carried out by nomads.
While investigating human settlements and stone-built leopard traps, our team also surveyed more than 60 cave in the escrapments and wadis of the study region. The mixed and turbated biological deposits of these caves, containing dung, bones, and nesting materials, held the key to understanding the changes in the mammalian foodweb through time. Animal bones of the local top-predators (leopards) and their favorite prey (hyrax and ibex) that accumulated in the caves can be dated using radiocarbon to provide a notion of the change in the relative abundance of each species through time. Our analysis of the radiocarbon results suggested that the leopard population suffered a precipitous decline during the millennia of human settlement and intensive hunting, while the hyrax and ibex populations burgeoned. This trophic cascade effect is supported by preliminary genetic results. Upon their final publication, we will have completed our mission with success — leaving behind us a lot of questions and future trails to follow.
Our work has been made available to the public through publication in scientific venues, including the Proceedings of the National Academy of Science (PNAS), Scientific Reports, Journal of Human Evolution, and Quaternary Science Reviews, and has been reported in online and physical scientific meetings and conferences.
While investigating human settlements and stone-built leopard traps, our team also surveyed more than 60 cave in the escrapments and wadis of the study region. The mixed and turbated biological deposits of these caves, containing dung, bones, and nesting materials, held the key to understanding the changes in the mammalian foodweb through time. Animal bones of the local top-predators (leopards) and their favorite prey (hyrax and ibex) that accumulated in the caves can be dated using radiocarbon to provide a notion of the change in the relative abundance of each species through time. Our analysis of the radiocarbon results suggested that the leopard population suffered a precipitous decline during the millennia of human settlement and intensive hunting, while the hyrax and ibex populations burgeoned. This trophic cascade effect is supported by preliminary genetic results. Upon their final publication, we will have completed our mission with success — leaving behind us a lot of questions and future trails to follow.
Our work has been made available to the public through publication in scientific venues, including the Proceedings of the National Academy of Science (PNAS), Scientific Reports, Journal of Human Evolution, and Quaternary Science Reviews, and has been reported in online and physical scientific meetings and conferences.
The analysis of Holocene human settlement patterns vis-a-vis wild animal community structure in the same region over a period of millennia has never been attempted before and is a major leap beyond the state of the art. Our radiocarbon analysis results are still waiting for more support from ancient DNA based population reconstructions. Our preliminary results in this field have been only partially published to date, but support the trophic cascading scenario observed in the radiocarbon date modelling.