1. The simplification of agricultural landscapes through the increase in cropped area has caused the loss of habitats for many species that fulfil important ecosystem services such as pest control and production. Evidence for detrimental effects on ecosystem services is scarce, particularly in tropical regions.
2. We studied the effect of the percentage of cropped land in the landscape and altitude in tropical agro-ecosystems in relation to crop pest regulation and yield. In the Colombian Andes, we established potato Solanum tuberosum plots along gradients of altitude and increasing proportion of cropped area to assess the effects on herbivores, their natural enemies, potato production and overall biodiversity.
3. Increasing altitude and percentage cropped land reduced the richness and abundance of herbivores and their natural enemies, except for the specialist Guatemalan potato moth Tecia solanivora, which showed the opposite response.
4. Potato yield was negatively affected by the presence of the Guatemalan potato moth, which increased in density as the percentage of cropped land and altitude increased. Other herbivores and natural enemies did not affect yield.
5. Synthesis and applications. Tropical landscapes at lower altitude or with smaller areas of cropped land suffered less from the presence of the potato moth, which had a negative effect on yield. Our results suggest that conservation of natural habitats like the endangered Andean ecosystems would benefit farmers through ecosystem services such as reduced pest damage, higher yield and increased functional biodiversity.