For the past few years, these parks have been the subject of noise monitoring and analysis. Initially, the catalyst was a supplemental environmental impact analysis led by the Air Force and the Federal Aviation Administration (FAA) and related to the proposal to convert the former Homestead Air Force Base, devastated by Hurricane Andrew in 1992, into a major single-runway, civilian airport. The issue has evolved into one of soundscape protection as the parks came to recognize that all human-caused noise was the problem, not just noise from aircraft.
Monitoring began in 1997 when the National Park Service sent a contractor into the field to collect the first scientific information on the nature and magnitude of natural sounds and some of the sources of human-caused noise intrusions in Everglades and Biscayne. Shortly thereafter the Federal Aviation Administration collected data in the area using a different method. Unfortunately, both methods have faults. The FAA approach, in particular, was keyed principally to the collection of data on aircraft noise, not on the levels of quiet the National Park Service seeks to protect. Another complication was trying to extrapolate noise data from the collection points to broader areas for the purpose of defining a park’s soundscape.
In November the NPS contractor went back into the field. This time, in addition to conducting hour-long monitoring at six sites missed by the Federal Aviation Administration, the contractor set up unattended monitoring stations to collect data on diurnal variations in noise level. These data, coupled with the previous data, have begun to provide some answers.
A combination of unattended monitoring and targeted monitoring to establish daily and seasonal noise variations, and to identify the nature and levels of intrusive noise, is proving to be a better sampling strategy. The National Park Service is drafting a manual describing this method and, in 1999, plans to define a credible process for describing a park’s soundscape based on disparate data. Additionally, a statistic called “L90,” the sound level exceeded 90% of the time, is a useful estimate of the natural soundscape, particularly under relatively noisy conditions. A policy is being drafted that spells out obligations of the National Park Service to inventory, monitor, and protect the soundscape. Many concepts related to soundscape preservation are already discussed in the NPS education package “The Nature of Sound,” and a forthcoming NPS director’s order will provide further direction on this issue. Finally, Biscayne, Everglades, and Big Cypress are in various stages of developing noise management plans that detail what can and must be done to protect their soundscape resources.
Photo Credit: © Jeff Selleck
bill_schmidt@nps.gov
Special Assistant to the Associate Director, Natural Resource Stewardship and Science, Washington, D.C.
MELALEUCA CONTROL
CONTINUES
Big Cypress National Preserve (Florida) continues to succeed in its partnership with Dade County and the Florida Department of Corrections for the control of melaleuca. At a cost of $220,000 in 1998, the partners re-treated 701,736 seedlings and resprouts of the nonnative tree species on 35 square miles of infested lands treated initially in 1997. The preserve also found matching funds from the Miami–Dade County Wetland Trust Funds for initial melaleuca treatments through FY 1999. A private contractor is available to the preserve and to Everglades National Park for five years to carry out the control effort.
Back to Chapter 4: Resource Disturbances
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