Extinction risks and mitigation for a megaherbivore, the giraffe, in a human‐influenced landscape under climate change

Abstract

Megaherbivores play “outsized” roles in ecosystem functioning but are vulnerable to human impacts such as overhunting, land‐use changes, and climate extremes. However, such impacts—and combinations of these impacts—on population dynamics are rarely examined using empirical data. To guide effective conservation actions under increasing global‐change pressures, we developed a socially structured individual‐based model (IBM) using long‐term demographic data from female giraffes (Giraffa camelopardalis) in a human‐influenced landscape in northern Tanzania, the Tarangire Ecosystem. This unfenced system includes savanna habitats with a wide gradient of anthropogenic pressures, from national parks, a wildlife ranch and community conservation areas, to unprotected village lands. We then simulated and projected over 50 years how realistic environmental and land‐use management changes might affect this metapopulation of female giraffes. Scenarios included: (1) anthropogenic land‐use changes including roads and agricultural/urban expansion; (2) reduction or improvement in wildlife law enforcement measures; (3) changes in populations of natural predators and migratory alternative prey; and (4) increases in rainfall as predicted for East Africa. The factor causing the greatest risk of rapid declines in female giraffe abundance in our simulations was a reduction in law enforcement leading to more poaching. Other threats decreased abundances of giraffes, but improving law enforcement in both of the study area's protected areas mitigated these impacts: a 0.01 increase in giraffe survival probability from improved law enforcement mitigated a 25% rise in heavy rainfall events by increasing abundance 19%, and mitigated the expansion of towns and blockage of dispersal movements by increasing abundance 22%. Our IBM enabled us to further quantify fine‐scale abundance changes among female giraffe social communities, revealing potential source–sink interactions within the metapopulation. This flexible methodology can be adapted to test additional ecological questions in this landscape, or to model populations of giraffes or other species in different ecosystems.

The contribution of community-based conservation models to conserving large herbivore populations

“…Especially for the central part of the ecosystem (Tarangire NP, Burunge WMA, and Manyara Ranch), population trends of the target species were mostly either stable or indicated population growth over time. This mirrors data from photographic mark-recapture studies of both wildebeest, showing that their population in the ecosystem has stabilized since the early 2000s 34 , as well as giraffe, whose populations in Manyara Ranch and much of Tarangire NP were stable from 2012–2016 37 . Our population trend estimates also align with results of a photographic mark-recapture study conducted from 2012 to 2016, indicating a slight decrease in the giraffe population over that time frame in Burunge WMA 37 (Fig.…”

“…This mirrors data from photographic mark-recapture studies of both wildebeest, showing that their population in the ecosystem has stabilized since the early 2000s 34 , as well as giraffe, whose populations in Manyara Ranch and much of Tarangire NP were stable from 2012–2016 37 . Our population trend estimates also align with results of a photographic mark-recapture study conducted from 2012 to 2016, indicating a slight decrease in the giraffe population over that time frame in Burunge WMA 37 (Fig. 2 c); our more recent data suggest that this trajectory has since reversed (Fig.…”

Activitybudget and foraging patterns ofNubian giraffe (Giraffa camelopardalis camelopardalis) in Lake Nakuru National Park, Kenya

“…Research on giraffe foraging at LNNP provides additional insights into the dietary flexibility and adaptability of giraffe, given that LNNP is on the periphery of a sprawling urban city. Urban sprawl and obstruction of giraffe dispersal patterns may limit their ability to move to suitable habitats and resources, affecting their survival and population dynamics (Bond et al., 2023). The park, like other enclosed ecosystems, has unique challenges, like habitat deterioration, competition for resources, heightened vulnerability to environmental shifts and increased risk of predation (Bond et al., 2023; Brenneman et al., 2009; Dharani et al., 2009; Gathuku et al., 2021; Muller, 2018).…”

“…Urban sprawl and obstruction of giraffe dispersal patterns may limit their ability to move to suitable habitats and resources, affecting their survival and population dynamics (Bond et al., 2023). The park, like other enclosed ecosystems, has unique challenges, like habitat deterioration, competition for resources, heightened vulnerability to environmental shifts and increased risk of predation (Bond et al., 2023; Brenneman et al., 2009; Dharani et al., 2009; Gathuku et al., 2021; Muller, 2018). Giraffe need a large home range to acquire resources and restricting them to a park can affect their activity time budget and overall survival (Brenneman et al., 2009; Obari, 2014; van der Jeugd & Prins, 2000).…”