Abstract
Freshwaters provide valuable habitat and important ecosystem services but are threatened worldwide by habitat loss and degradation. In Southeast Asia, rainforest streams are particularly threatened by logging and conversion to oil palm, but we lack information on the impacts of this on freshwater environmental conditions, and the relative importance of catchment versus riparian‐scale disturbance. We studied 16 streams in Sabah, Borneo, including old‐growth forest, logged forest, and oil palm sites. We assessed forest quality in riparian zones and across the whole catchment and compared it with stream environmental conditions including water quality, structural complexity, and organic inputs. We found that streams with the highest riparian forest quality were nearly 4 °C cooler, over 20 cm deeper, had over 40% less sand, greater canopy cover, more stored leaf litter, and wider channels than oil palm streams with the lowest riparian forest quality. Other variables were significantly related to catchment‐scale forest quality, with streams in the highest quality forest catchments having 40% more bedrock and 20 times more dead wood, along with higher phosphorus, and lower nitrate‐N levels compared to streams with the lowest catchment‐scale forest quality. Although riparian buffer strips went some way to protecting waterways, they did not maintain fully forest‐like stream conditions. In addition, logged forest streams still showed signs of disturbance 10–15 years after selective logging. Our results suggest that maintenance and restoration of buffer strips can help to protect healthy freshwater ecosystems but logging practices and catchment‐scale forest management also need to be considered.
Highlights
Freshwater ecosystems are intricately linked with their surrounding terrestrial habitats
We found that streams with the highest riparian forest quality were nearly 4 °C cooler, over 20 cm deeper, had over 40% less sand, greater canopy cover, more stored leaf litter, and wider channels than oil palm streams with the lowest riparian forest quality
We show that rainforest logging and oil palm agriculture affect a wide range of stream environmental conditions, that both riparian and catchment‐scale forest quality are important in moderating these impacts, and that different stream conditions are affected by disturbance at different scales
Summary
Freshwater ecosystems are intricately linked with their surrounding terrestrial habitats. Freshwater ecosystems provide essential services for people, including water for drinking, homes, agriculture, and industry, as well as food resources such as fish and crustaceans. They provide habitat for 6% of the world's species (Dudgeon et al, 2006), of which it is estimated that 10,000–20,000 are currently at risk of extinction (Strayer & Dudgeon, 2010; Vörösmarty et al, 2010). If the ecosystems and services provided by freshwaters are to be maintained and managed effectively, it is essential that the impacts of land‐use change and degradation on waterways are understood
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have