Evaluating ecosystem service trade-offs along a land-use intensification gradient in a mountain watershed in central Veracruz, Mexico

Montane forests provide important local and global ecosystem services (ES). Concern over rapid land cover/land use (LCLU) change has led to the recent proliferation of Payments for Hydrologic Services (PHS) policies to incentivize forest conservation. The narrow focus of PHS programs on water resources may come at the expense of other ES, yet these potential tradeoffs are rarely quantified using field-based measurements, severely limiting effective policy design. This study assesses the synergies and tradeoffs between three regulating (hydrologic cycling, water purification, climate regulation) and one supporting (biodiversity) ecosystem services in the tropical montane forests of Veracruz, Mexico.

We quantified 10 ES indicators across 3 forests ages (primary, mature secondary, young secondary), two coffee systems (high and low intensity), two pasture systems (high and low intensity), and sugar cane. We expected that (1) LCLU types with greater tree cover would have higher ES provisioning and (2) clear positive relationships would exists between hydrologic regulation, water quality, carbon, and biodiversity services.

We found that primary forests improve hydrological services having high base flow, peak flow and soil conductivity. Primary forests also store greater amounts of carbon and harbor greater biodiversity. For shade-grown coffee sites, we surprisingly find that ES provisioning is low with poor water quality, reduced hydrological services, and low carbon storage. Further, we observed synergies across many ES where management of one would improve provisioning of multiple ES, specifically between flow, carbon storage, and biodiversity. Unexpectedly, no relationship was observed between hydraulic regulation and water quality; i.e. improved flow regimes did not correspond to improved water quality. Our results underscore the value of site-specific empirical research in addressing assumptions about the relationship between LCLU and ES provisioning, which may not be valid under a range of different contexts. As more studies reveal patterns around synergies or tradeoffs between services, a clearer picture of these complex relationships can be established, allowing for more informed PHS design to maximize ES benefits.