Agricultural expansion is the predominant mode of tropical land cover change, leading to profound alterations in vegetation, carbon stocks, and freshwater systems. The dynamics of these ecosystem changes depend on land cover trajectories preceding agricultural conversion. Assessing ecological outcomes from major land cover transitions is therefore critical for reducing uncertainties about how food production affects the human-natural system. This dissertation examines the influence of oil palm plantation expansion on land cover and ecosystem processes at nested regional (Kalimantan, 538,346 km²) and local (Ketapang, 12,038 km²) scales.
Major regional land covers were classified from a timeseries of Landsat satellite images. Using a spatially-explicit model of oil palm expansion, future land cover change was assessed under various scenarios. Carbon emissions from plantations were estimated with a carbon bookkeeping model of above- and below-ground carbon flux from deforestation, forest degradation, vegetation regrowth, and peatland soil burning and draining. To discern the effects of plantation development on freshwater ecosystems, streams draining watersheds dominated by forests, agroforests, and oil palm were monitored from 2008-2012.
From 1990-2010 across Kalimantan, ∼70% of oil palm expansion cleared intact and logged forests. In Ketapang, plantation land sources exhibited distinctive temporal dynamics, composing mostly forests on mineral soils from 1994-2001, shifting to peatlands from 2008-2011. If all government-allocated plantation leases are developed, oil palm will occupy 34% of Kalimantan lowlands (< 300m) outside of protected areas.
Such rapid plantation expansion affects ecological processes at multiple scales. Locally, results indicate that plantation land use significantly alters stream metabolism, temperature, and sediment loads; moreover, such changes persist as oil palm matures. Regionally, Kalimantan oil palm plantations are projected to contribute 18-22% (0.12-0.15 GtC y-1) of Indonesia's 2020 CO2 equivalent emissions. Analysis of Ketapang scenario model outcomes suggests that emissions mitigation will require protection of existing carbon stocks. While prohibiting intact and logged forest and peatland conversion to oil palm reduces emissions only 4% below BAU, protecting intact and logged forests achieves 21% carbon emissions reductions.
These findings demonstrate significant trade-offs between large-scale tropical agricultural production and maintenance of ecosystem processes crucial to human well-being across local-to-global scales.
|Advisor:||Curran, Lisa M., Seto, Karen C.|
|Commitee:||Doolittle, Amity, Raymond, Peter|
|Department:||Forestry and Environmental Studies|
|School Location:||United States -- Connecticut|
|Source:||DAI-B 74/05(E), Dissertation Abstracts International|
|Subjects:||Natural Resource Management, Land Use Planning, Sustainability, Environmental science, Remote sensing|
|Keywords:||Borneo, Carbon flux, Land cover change, Land use change, Palm plantations, Tropical agriculture, Water quality|
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