Contribution of dung beetles to cattle productivity in the tropics: A stochastic-dynamic modeling approach

Dung beetles provide different services to agroecosystems. Previous economic assessment of this insect group highlights their importance in temperate zones using linear models or ecosystem services frameworks. This paper proposes a stochastic-dynamic model to simulate dung production and degradation in order to estimate the contribution of dung beetles to dual-purpose cattle production in the tropical grasslands of Veracruz, Mexico. The model allowed for estimation of sampling distributions of dung occurrence in the field, the coverage area, nitrogen burial, and maintenance of clean grasslands and their economic benefits. Contributions of dung beetles are expressed as 95% confidence intervals. Dung beetles removed from 56.2 to 116.9 depositions ha-1 d-1 and the efficiency in dung removal was between 65 to 69%. At the grassland scale, dung beetles cleaned an area from 8.5 to 26.9 m2 ha-1 d-1. Nitrogen burial ranged from 32.2 to 136.2 kg ha-1 y-1. The clean area maintained annually varied between 31 to 98% of the pastures. The annual benefit per animal unit ranged between US$149.1 to US$ 423.6 and at state level the benefit (US$ × 10E6) was between 140.6 and 455.8. The most important economic contribution was maintaining clean areas (71.4%), then by incorporating nitrogen as fertilizer (28.3%), and last in milk and meat benefits (< 1%). The model allowed for the representation of the natural variability of some key factors involved in dung processing by beetles related to dual-purpose cattle production.