The Madingley General Ecosystem Model predicts bushmeat yields, species extinction rates and ecosystem-level impacts of bushmeat harvesting

Abstract

Traditional approaches to guiding decisions about harvesting bushmeat often employ singlespecies population dynamic models, which require species-and location-specific data, are missing ecological processes such as multi-trophic interactions, cannot represent multispecies harvesting, and cannot predict the broader ecosystem impacts of harvesting. In order to explore an alternative approach to devising sustainable harvesting strategies, we employ the Madingley General Ecosystem Model, which can simulate ecosystem dynamics in response to multi-species harvesting given nothing other than location-specific climate data. We used the model to examine yield, extinctions, and broader ecosystem impacts, for a range of harvesting intensities of duiker-sized ectothermic herbivores. Duiker antelope (such as Cephalophus callipygus and Cephalophus dorsalis) are the most heavily hunted species in sub-Saharan Africa, contributing 34%-95% of all bushmeat in the Congo Basin. Across a range of harvesting rates, the Madingley model gave estimates for optimal harvesting rate, and extinction rate, that were qualitatively and quantitatively similar to the estimates from singlespecies Beverton-Holt model. Predicted yields were somewhat greater (around 5 times, on average) for the Madingley model, which would be expected given that the Madingley simulates multi-species harvesting from an initially pristine ecosystem. This match increased the degree of confidence with which we could examine other predictions from the ecosystem model, as follows. At medium and high levels of harvesting of duiker-sized herbivores, there were statistically significant, but moderate, reductions in the densities of the targeted functional group; increases in small-bodied herbivores; decreases in large-bodied carnivores;and minimal ecosystem-level impacts overall. The results suggest that general ecosystem models such as the Madingley model could be used more widely to help estimate sustainable harvesting rates, bushmeat yields and broader ecosystem impacts across different locations and target species.

Towards an ecosystem model of infectious disease

“…By sourcing environmental input data from closely monitored sites experiencing changes in land use over a defined period, and aligning this to the time steps over which simulations occur, the predicted responses of host and parasite cohorts could be evaluated against empirical data on vegetation, host and parasite abundance. A term that simulates harvesting of certain wild animal host cohorts could then be added to the model to investigate how specific changes in trophic structure influence parasite dynamics 96 . As an emergent property of the GEpM, the relative abundance and biomass of the (NS)-RNA virus cohort could estimate 'pathogen pressure' for each grid cell on which the model is runrepresenting the quantity of (NS)-RNA viruses in wildlife to which humans could be exposed at a given point in space and time.…”

MadingleyR: An R package for mechanistic ecosystem modelling

“…This is because the terrestrial component of the model is further developed and more extensively tested (e.g. Bartlett et al., 2016; Barychka et al., 2020; Enquist et al., 2020; Harfoot et al, 2020; Hoeks et al., 2020; Newbold et al., 2020) compared with the marine component. The Madingley model does not include any interactions between the marine and terrestrial realms, making terrestrial simulations completely independent of processes occurring within the marine realm.…”

“…This is because the terrestrial component of the model is further developed and more extensively tested (e.g. Bartlett et al, 2016;Barychka et al, 2020;Enquist et al, 2020;Harfoot et al, 2020;Hoeks et al, 2020;Newbold et al, 2020) simulations completely independent of processes occurring within the marine realm.…”

“…Since the Madingley model was introduced, it has been used to examine human influence on ecosystem dynamics, such as the effect of land‐use change on ecological patterns (e.g. Bartlett et al., 2016), the impact of bushmeat harvesting on ecosystems (Barychka et al., 2019, 2020), and the impact of megafauna loss for ecosystem functioning (Enquist et al., 2020; Hoeks et al., 2020). The Madingley model has also been used to gain deeper insights into the mechanisms underlying macroecological patterns such as the Bergmann’s rule (Harfoot et al, 2020).…”

The Madingley general ecosystem model predicts bushmeat yields, species extinction rates and ecosystem‐level impacts of bushmeat harvesting

“…The Madingley model is publicly available on <https:// madingley.github.io/>. The simulation outputs will be deposited in DataDryad: <http://dx.doi.org/10.5061/ dryad.1g1jwstxh> (Barychka et al 2021).…”