Approaches to Sustainable Management of Deltas: Integrating Natural System Subsidies With Societal Needs in the Mississippi and Ebro Deltas.
This dissertation focuses on deltaic sustainability and its implications for management of deltas. Net primary productivity (NPP) was used to measure temporal changes in the ecological status of the Ebro and Mississippi Deltas. Human appropriation of net primary productivity (HANPP) was used as a measure of direct human use and dependence on deltaic productivity. In the Mississippi, NPP declined from 2500 g/m2/yr in 1900 to 2000 g/m2 /yr in 1990, with a decline to 1750 g/m2/yr expected by 2050. In the Ebro, total system NPP increased from 700 g/m2/yr to 1000 g/m2/yr due to agriculture. High HANPP of 35% reduced remaining NPP to 600 g/m2/yr. The natural energies and anthropogenic subsidies that maintain natural and human modified deltaic ecosystems were also analyzed. Results indicate that reduction of important natural energies result in higher economic costs and ecological decline. An energy analysis was used to estimate non-market values (e.g. storm protection, waste assimilation, and flood control) under various land cover scenarios. In the Mississippi, land loss has led to a decline in non-market values resulting in a total loss of $29.4 billion. Total non-market value is projected to decrease to $2.1 billion/yr. In the Ebro delta, conversion to agriculture resulted in a drop in total annual non-market value from $21 million to $11 million. The rate of return has decreased from the pristine to the present delta, indicating that more inputs are required to produce a smaller output. Utilizing natural energies is one way to manage deltas sustainably. I present a case study of the use of wetlands for wastewater treatment (WWT) for a shrimp processor in Dulac, LA. WWT results in ecological and economic benefits. The avoided cost economic analysis resulted in a capitalized cost savings of over $1.5 million for wetland treatment over conventional technology. Dominant socio-economic activities currently undermine critical sedimentary processes leading to geomorphic instability, impaired ecological sustainability, and ultimately result in negative economic consequences. Incorporation of natural systems energies into human activities, instead of fighting or diverting them, is the key to successful management of deltas.