Estimating Marginal Costs of Additional Water Flow from a Loblolly Pine Stand in South Georgia, United States

Abstract

Certain silvicultural operations enhance the flow of ecosystem services derived from forestlands. Monetary estimates of an increased flow of such services that can impact forest management decisions are generally lacking. Here we use a growth-and-yield model to estimate physical changes in water yield and assign monetary values to these changes under different regimes of forest thinning and planting density in a loblolly pine (Pinus taeda L.) stand located in South Georgia. The model is expanded to develop corresponding measures of water yield and net present value per each management scenario. Results show an expected inverse relationship between average annual water yield and economic rent. Further, the marginal costs associated with producing an extra liter of water (per unit area) decrease as thinning intensifies and planting density declines (US$1.35/kL to US$0.72/kL under a site index of 18.3 m and US$1.20/kL to US$0.66/kL, assuming a site index of 21.3 m) relative to our baseline scenario. We emphasize that a landowner’s profits may be negatively affected by the provision of improved water yield downstream as it competes with timber extraction. Monetary payments are needed to encourage the net production of water from existing loblolly pine stands in South Georgia, United States. Study Implications Silvicultural interventions (i.e., modifications to thinning and planting density rates) are likely to generate enhanced water flow to downstream users. Private landowners may have to be compensated for providing improved water services induced by select silvicultural operations because such operations impose costs to landowners. There are trade-offs in the provision of such ecosystem services as timber extraction, water flow, and carbon sequestration and such trade-offs should be taken into account while managing forestlands.

In‐Situ Quantification and Prediction of Water Yield From Southern US Pine Forests

“…Forward model applications include scenario analyses to predict changes in water yield with different forest management activities, short-term climate variation, and long-term climate change at spatial scales from forest stands to large watersheds. In the southeastern US and other regions facing increasing water shortages (Anandhi & Bentley, 2018;Sun, 2013), such region-specific models are critical for supporting water supply planning activities (Douglass, 1983) and the development and implementation of policy instruments that incentivize water yield as an important forest product (Bawa & Dwivedi, 2021;Susaeta et al, 2016Susaeta et al, , 2017. While coarser watershed and continental-scale models exist (e.g., the Water Supply Stress Index Model, WaSSI (Sun, Caldwell, et al, 2011)) and similarly offer estimates of water yield change with land use and climate scenarios, empirical predictions from in-situ observations are important for supporting and validating more region-and ecosystem-specific models.…”