Maisels, F. | bioRxiv Science

bioRxiv2023

Using a multiscale lidar approach to determine variation in canopy structure from African forest elephant trails.

Recently classified as a unique species by the IUCN, African forest elephants (Loxodonta cyclotis) are critically endangered due to severe poaching. With limited knowledge about their ecological role due to the dense tropical forests they inhabit in central Africa, it is unclear how the Afrotropics would change if forest elephants were to go extinct. Although their role as seed dispersers is well known, they may also drive large-scale processes that determine forest structure, through the creation of elephant trails and browsing the understory and allowing larger, carbon-dense trees to succeed. Multiple scales of lidar were collected by NASA in Lope National Park, Gabon from 2015-2022. Utilizing two airborne lidar datasets and one spaceborne lidar in an African forest elephant stronghold, detailed canopy structural information was used in conjunction with elephant trail data to determine how forest structure varies on and off trails. Forest above elephant trails displayed different structural characteristics than forested areas off trails, with lower canopy height, canopy cover, and different vertical distribution of plant mass. Less plant area density was found on trails at 1 m in height, while more vegetation was found at 12 m, compared to off trail locations. Trails with previous logging history had lower plant area in the top of the canopy.

ecology↗

bioRxiv2020

Predicting range shifts of African apes under global change scenarios

AimModelling African great ape distribution has until now focused on current or past conditions, whilst future scenarios remain scarcely explored. Using an ensemble forecasting approach, we predicted changes in taxon-specific distribution under future scenarios of climate, land-use and human population changes. LocationSub-Saharan Africa MethodsWe compiled occurrence data on African ape populations from the IUCN A.P.E.S. database and extracted relevant human-, climate- and habitat-related predictors representing current and future (2050) conditions to predict taxon-specific distribution under a best- and a worst-case scenario, using ensemble forecasting. Given the large effect on model predictions, we further tested algorithm sensitivity by considering default and non-default modelling options. The latter included interactions between predictors and polynomial terms in correlative algorithms. ResultsThe future distributions of gorilla and bonobo populations are likely to be directly determined by climate-related variables. In contrast, future chimpanzee distribution is influenced mostly by anthropogenic variables. Both our modelling approaches produced similar model accuracy, although a slight difference in the magnitude of range change was found for Gorilla beringei beringei, G. gorilla diehli, and Pan troglodytes schweinfurthii. On average, a decline of 50% of the geographic range (non-default; or 55% default) is expected under the best scenario if no dispersal occurs (57% non-default or 58% default in worst scenario). However, new areas of suitable habitat are predicted to become available for most taxa if dispersal occurs (81% or 103% best, 93% or 91% worst, non-default and default, respectively), except for G. b. beringei. Main ConclusionsDespite the uncertainty in predicting the precise proportion of suitable habitat by 2050, both modelling approaches predict large range losses for all African apes. Thus, conservation planners urgently need to integrate land-use planning and simultaneously support conservation and climate change mitigation measures at all decision-making levels both in range countries and abroad.

ecology↗