An increasing human-elephant conflict? Impact of African elephant on cultivated cashew trees

Elephants influence the structure and composition of African woodlands and, sometimes, damage cultivated trees in farms of local communities. Here, we evaluate the impact of elephant debarking on cultivated cashew trees (Anacardium occidentale) as the friction between farmers and elephant conservation is increasing. We quantified the effects of elephant debarking on tree survival, crown defoliation, and nut production by visiting elephant-damaged farms with cashew trees (n = 47 farms) along Sasawara National Forest (Tanzania). We also compared defoliation and nut production with nearby control trees (undamaged) in a paired designed. Our results reveal that elephants debarked a significant proportion of trees (36% of farms had some cashew trees damaged by elephants, with a mean of 17.3% damaged trees per farm), with a preference for medium-large tree sizes (> 20 cm of diameter at breast height). Tree mortality due to elephants was 4 trees (4.2% of the affected trees), which represents around 0.1% of the total number of trees in the affected farms. In the year of damage, elephant debarking caused no effect on defoliation whereas nut production was reduced only in trees with very high intensity of damage (> 60% of trunk circumference affected). However, a year after the damage, both defoliation and nut production were negatively affected but this effect was strongly dependent on the intensity of damage and tree diameter. These results may help reduce the social discomfort of cashew farmers and contribute to enhance human-elephant coexistence. However, further studies should analyze the future vulnerability of damaged trees to fires, pathogens or pests.