The economic value of watershed conservation

Abstract

Watershed conservation creates benefits within and beyond the management area of interest. Direct benefits are those realized in the watershed itself, such as improved water quality and quantity, and biodiversity protection. Additionally, the health of a watershed has profound implications on near-shore resources below its reaches, including beaches and coral reefs. This chapter reviews the major benefits of watershed conservation and discusses the economic value of these activities. Within the watershed itself, conservation activities assist in protecting important groundwater sources by maintaining healthy canopies, native plant cover, reducing erosion, and fending off nuisance plant and animal species that degrade the system. These activities are a vital part of overall watershed maintenance and are reviewed in the introduction to this volume. Systems that often are excluded from the discussion of watershed management are those downstream from the area of interest. Improved watershed health leads to less runoff to ecosystems below and therefore cleaner and more valuable beaches and reefs. Perhaps the most direct benefit from tropical watershed conservation is that of aquifer recharge. The Hawaiian island of Oahu gets about 90% of its fresh water supply from groundwater. Alternative production techniques such as desalination are costly and postponement of their need is a valuable policy goal. Postponement can occur through the supply side by maintaining or potentially enhancing forest quality. The Ko`olau conservation district is a 97,760 acre area along the Ko`olau mountain range running the entire windward (Eastern) side of the island. There are hundreds of inches of rain each year in some locations, and the general trend is for high levels of rainfall along the crest of the range declining with elevation. The form and composition of the forest in large part determines how much of the water will run off, how much sediment it will carry, and how much will recharge the aquifers from which Oahu draws its water supply. Kaiser et al. (1999) calculate that the net present value lost from a decrease in recharge of 41 MGD to the Pearl Harbor aquifer may be between $1.42 billion and $2.63 billion dollars, depending on the assumptions made regarding the social discount rate. If the current levels of groundwater recharge are maintained, the scarcity rents will rise from $0.6 thousand gallons in year 2000 to nearly $3 in year 2072. On the other hand, if the forest damage reduces the recharge by 41 MGD, the scarcity rents in year 2000 jump to over $1 thousand gallons and rise to nearly $3 by 2057. They also calculate that if recharge to the aquifer from the Ko`olaus ceased altogether, the reduction of inflow to the Pearl Harbor aquifer would be approximately 133 MGD. The lost net present value from such a disruption would amount to $4.57 to $8.52 billion. Biodiversity and aesthetics are among the other direct benefits provided by tropical watersheds.

Addressing Gender Inequities in Forest Science and Research

“…Brooks A. Kaiser is a professor of environmental and resource economics at the University of Southern Denmark. Her research in forests and forested watersheds spans questions of resource use and governance ranging in time and space, from how Athens met its timber requirements in the Classical Era (509-322 BCE) to the evolution and value of multifaceted Hawaiian forested watershed resources and their conservation over the past century [79][80][81], as well as threats to these values from invasive species [82], to how requirements for environmental impact statements in the National Environmental Protection Act (NEPA, 1970) affected resource allocations and decision-making in US National Forests [83].…”

Optimal and Sustainable Groundwater Extraction

“…Optimal groundwater management should therefore incorporate investment in watershed conservation capital in order to enhance the recharge capacity of the aquifer. Capital expenditures might include investment in fencing for feral animals, removal of invasive plants, reforestation of native flora, or construction of engineering structures designed to increase infiltration [18].…”