Aquatic Ecosystem Impacts of Land Sharing Versus Sparing: Nutrient Loading to Southeast Asian Rivers

TitleAquatic Ecosystem Impacts of Land Sharing Versus Sparing: Nutrient Loading to Southeast Asian Rivers
Publication TypeJournal Article
Year of Publication2017
AuthorsKoning, A. A., Moore J., Suttidate N., Hannigan R., and McIntyre P. B.
JournalEcosystems
Volume20
Issue2
Number of Pages393-405
Date PublishedMar
Type of ArticleArticle
Reprint Number1432-9840
LTER Accession NumberWOS:000395868200019
Keywordsagricultural land; n-p; nitrogen; limitation; intensification;, Environmental Sciences & Ecology, land-use change; nutrient limitation; rare earth element; swidden; Chao, Phraya; Mekong; Salween, rare-earth-elements; terrestrial ecosystems; swidden cultivation;, stoichiometry; phosphorus
Abstract

As world food demand continues to increase, two broad strategies for agricultural production have been widely discussed: land sparing and land sharing. Reflecting tradeoffs between the extent and intensity of agricultural use, land sparing maximizes the ratio of conserved to agricultural land, whereas land sharing allows more extensive, nature-friendly transformation of the agroecological matrix. Freshwater ecosystems are rarely considered in weighing these strategies, despite being strongly affected by land-use change. Here we analyze how shifting from extensive to intensive agricultural practices is altering dry season riverine nutrient availability and algal growth in upland Southeast Asia, which is experiencing rapid conversion from swidden-or shifting-cultivation to fertilized row crops. In situ algal growth assays and nutrient concentration data from eleven catchments representing a spectrum of land use and population densities show that intensive agriculture is associated with significantly elevated nitrate concentrations but no shift in phosphorus. As a result, nitrogen to phosphorus ratios increases dramatically, shifting algal growth toward colimitation by nitrogen and phosphorus. Geochemical analysis of suspended solids suggested comparable geological inputs across basins, but dissolved rare earth elements reveal that inorganic fertilizers are changing water chemistry in parallel with land use. Taken together, our analyses suggest that the transition from low-input land-sharing management (swidden) to high-input land-sparing practices (intensive row-crop agriculture) underway in Southeast Asia has profound consequences for river ecosystems. Such nutrient loading can affect river productivity and food webs, suggesting that land-use conservation strategies for Southeast Asia need to account for impacts on freshwater ecosystems.

URL<Go to ISI>://WOS:000395868200019
Print Copy LocationEcosystems