ROCI: Case Studies

Socioeconomic Benefits of Adaptive Nutrient Management 

A pork wholesaler doing business in North Carolina wants to improve downstream water quality and minimize the cost of livestock feed production by reducing fertilizer runoff from cultivated fields.

Watersheds in the coastal plain of North Carolina receive an estimated 134,000 Mg of nitrogen and 44,000 Mg of phosphorus runoff annually from excess fertilizer applied in agricultural areas and urban development. Agriculture contributes 92% of the nitrogen and 96% of the phosphorus delivered from watershed to stream. We used information from studies of agricultural practices in North Carolina’s Coastal Plain, and the InVEST geospatial mapping and economic modeling program to evaluate the role that improved fertilizer management and the nutrient processing capacity of riparian buffers and Palustrine wetlands could play in meeting regional water quality goals.

We measured the response of each watershed to three alternative nutrient management strategies and quantified the improvement in water quality of each in terms of avoiding the cost of artificial water treatment. Decreasing nutrient source load on selected crops reduced the net export of nitrogen 3% and phosphorus 1% when compared to baseline assessments.

Placing riparian buffers adjacent to all surface waters reduced nitrogen export 7% and phosphorus export 9%. Siting Palustrine wetlands above surface water intake structures reduced nitrogen export 6% and phosphorus 7% in those watersheds. We calculated the economic benefits of each nutrient management strategy in terms of the avoided cost of artificial water treatment. The addition of riparian buffers in each watershed provided the largest economic benefit with a median cost savings of $33B annually.

Analysis showed that ambitious nutrient reductions needed to address downstream nutrient pollution will only be achieved with significant investment in practices which can restore nutrient processing capacity to the landscape. Regional improvements in nutrient use efficiency, combined with a diverse portfolio of nutrient removal practices implemented over 7 million hectares across the Coastal Plain allows us to achieve a reduction in nutrient runoff while providing cost savings to municipalities in wastewater treatment expenditure.

Estimating the Socioeconomic Value of Open Space Nature Preserves

We benefit from many of the services provided by nature’s ecological functions that contribute to air and water quality, and the wildlife-associated recreational opportunities offered by species diversity. Working with valuation models and geospatial data, this study assessed the socioeconomic value of conserving publicly managed open space through economic simulation models designed to estimate benefits based on the biophysical properties of landcover and the protection of biodiversity through species’ habitat conservation.

This assessment provided information intended to inform policy decisions by estimating both market and non-market values associated with the benefits provided to residents who directly or indirectly use these resources. The intent of this study is to heighten awareness of open space property values expressed in terms of their biological, ecological, geological and social worth. The InVEST program was used to model the benefits of biological carbon removal and nutrient retention.  The Wildlife Habitat Benefits Estimation Toolkit was used to quantify the benefits of biodiversity and wildlife-associated recreation based on a willingness to pay to observe wildlife or simply know that a species exists.

The benefits of carbon sequestration and storage were expressed as the avoided social cost of carbon. The benefits of nutrient retention were expressed as the replacement cost of biological filtration with artificial water treatment. The annual benefit of carbon sequestration averaged $612/ha. The lifetime benefit of carbon storage averaged $9,186/ha. The 2.3 million tons of carbon stored is five orders of magnitude greater than the 30 tons of nutrients retained. The social cost of carbon used to quantify the benefit of carbon sequestration and storage was $60/ton.

The annual benefits of nutrient retention averaged $63/ha for nitrogen and $111/ha for phosphorus. The cost of artificial water treatment used to quantify the benefit of nutrient retention averaged 18 cents/ton.