What effect do tree plantations have on the diversity of native organisms? Some studies show that plantations reduce the diversity and abundance of certain taxa, while other studies suggested that plantations help to conserve biodiversity. Pine and eucalyptus plantations are among the most widespread exotic plantations worldwide, and they have negative effects on many taxa. But how do they affect amphibian diversity and abundance? We barely know. We therefore tallied up the number of amphibian taxa and their abundance from 18 ponds in patches of native oak forests, pine or eucalypt plantations. We also quantified water quality by measuring its physicochemistry and identifying the macroinvertebrates present in each pond. There were significantly fewer amphibian species in tree plantations than in native forest. Compared to native forest, the total density of amphibians was also significantly lower in eucalypt, but not pine, plantations. Species varied in the effects of plantations on their presence and abundance. We suggest that the decline in the presence and abundance of amphibians in plantations is linked to the physicochemical of pond water, combined with the relatively low presence of invertebrate. It seems likely that earlier desiccation, greater toxicity, and poor quality detritus in ponds in plantation are key drivers of species decline. The effects of these drivers are expected to worsen as climate change continues.