Agricultural Land Use Change Alters Parasitic Infection Cycles in Tadpoles of Hyla versicolor

Emerging infectious diseases are a global threat to biodiversity and can often act in tandem with other stressors to drive population declines. Agriculture, both conventional and organic, alters landscapes, which can affect various aspects of the parasitic infection cycle. However, the widespread adoption of organic agriculture may not effectively mitigate the impacts of agriculture on parasitic infections, yet little work has examined this. We investigated the effects of different agricultural practices on Helisoma trivolvis snail abundance and parasite (Echinostoma trematode) prevalence and infection intensity in tadpoles of Hyla versicolor across 19 ponds. We collected snails and tadpoles from three types of ponds: natural ponds with minimal agricultural influence, organic ponds with no nearby conventional agriculture, and conventional agricultural ponds. We found that natural ponds exhibit higher canopy cover and lower temperatures compared to conventional and organic ponds, while there was no significant difference in canopy cover between the latter two types. Pond type significantly predicted parasite prevalence in tadpoles of Hyla versicolor, with natural ponds having the lowest prevalence. However, there was no significant difference in prevalence between conventional and organic ponds, indicating that despite the effort to mitigate costs to farming on biodiversity, organic farming is not outperforming conventional farming at decreasing infection loads. Instead, canopy cover and associated changes in temperature may play a greater role in infection abundance. If this is the case, then maintaining canopy cover within 500 m of a pond may be the first step to minimizing infection abundance in tadpoles.