I am happy to share another study about a region I know little about: The Gran Chaco.
The Gran Chaco is a massive plain that encompasses north-central Argentina, western Paraguay, southeast Bolivia, and a small part of Brazil. There appear to be some uncertainties about how large the Chaco is, but the general range of figures is between 800,000 – 1.1 million km2 (Prado, 1993; Romero-Muñoz et al., 2018). That is more than twice the size of California (WWF, 2018).
Despite its vastness, the Chaco is undergoing rapid deforestation and defaunation (loss of medium and large wildlife); largely driven by the expansion of agriculture (WWF, 2018; Romero-Muñoz et al., 2018; The Nature Conservancy, 2018). The Chaco’s top predator, the jaguar (Panthera onca), is one of the creatures under threat.
Alfredo Romero-Muñoz and his colleagues set out to map the extent of the jaguar’s habitat degradation in the Gran Chaco between 1985-2013. In addition, they sought to determine whether hunting or habitat loss were most responsible for the cats’ decline in the region.
Hunting and habitat loss often intersect. When a patch of forest is cleared, for example, jaguars then have less cover and natural prey; making them more vulnerable to human hunting and conflict with people. Furthermore, the extension of roads into remote locations gives hunters access to harder-to-reach places.
However, excessive hunting can deplete an area of its large mammals before habitat loss does (Galetti & Dirzo, 2013; Jorge, Galetti Ribeiro, & Ferraz, 2013; Thoisy et al., 2016). To determine how habitat loss and hunting interact in the Chaco, Romero-Muñoz et al. (2018) mapped the expansion of both threats over the same time period (1985-2013). Theirs was the first study to do so.
To obtain their findings, the researchers amassed a large amount of data concerning: jaguar occurrences in the Chaco, predictors of key resources that determined the quality of jaguar habitat, and where people had killed jaguars. They used a machine learning approach to determine how threats to jaguars had changed over time (Romero-Muñoz et al., 2018).
Romero-Muñoz et al.’s (2018) results were both alarming and hopeful. For one, they found that jaguars had lost a huge amount of habitat between 1985-2013. Jaguar core areas – which are habitat patches with plentiful resources and low hunting pressure – declined by 33%. That comes out to 82,400 km2, or an area the size of Austria (Romero-Muñoz et al., 2018).
Habitat fragmentation also increased between 1985-2013, which makes jaguars more vulnerable to inbreeding depression and human hunting.
Concerning hunting, Romero-Muñoz et al. (2018) found that ‘sinks’ and ‘attractive sinks’ (areas where jaguars are more likely to be killed by humans) both grew by about 27% during their study period (p. 8). Most of the jaguar’s range in the Chaco consisted of sinks and attractive sinks by 2013.
Based on these results, hunting has expanded faster than habitat loss in the Chaco. By 2013, hunting impacted an area 20% larger than low resource availability – although the two threats acted together over 29% of the jaguar’s range (Romero-Muñoz et al., 2018, p. 11). But there is still time to act.
A substantial portion of jaguar core habitat remains in the Chaco, mostly close to international borders. At the same time, only 9.1% of the Chaco is formally protected. Since protected areas (especially large ones) lost proportionally less jaguar habitat than unprotected areas, this presents an opportunity.
Establishing reserves along international borders would strengthen the Chaco’s protected area network, and it could also bolster habitat connectivity in the region.
Moreover, hunting appears to be the primary threat to jaguars in the Chaco. This can be addressed. Working with local people to increase tolerance for jaguars, discouraging hunting, and expanding protected areas could all reduce the pressure on jaguars.
In summary, Romero-Muñoz et al. (2018) learned that jaguars are faring worse in the Chaco than previously thought; areas with low resource availability and high hunting pressure both expanded considerably between 1985-2013. Luckily, all is not lost. By quickly establishing protected areas along international borders and reducing hunting, the Chaco’s jaguars can still be saved.