Full ecoregional plan - Conservation Gateway
Full ecoregional plan - Conservation Gateway Full ecoregional plan - Conservation Gateway
PLANNING METHODS FOR ECOREGIONAL TARGETS: FRESHWATERAQUATIC ECOSYSTEMS AND NETWORKS *IntroductionFreshwater biodiversity conservation is vital to The Nature Conservancy’s mission ofbiodiversity conservation. Compelling documentation of the perils facing freshwater biodiversityindicate that many of the most endangered species groups in the U.S. are dependent onfreshwater resources. Approximately 70% of freshwater mussels, 52% of crayfish, 42% ofamphibians and 40% of freshwater fish are classified as vulnerable or higher with respect toextinction risks. Additionally, water itself is a critical resource to terrestrial species andecosystems and its patterns of drainage and movement have shaped the larger landscape in theNortheast.Freshwater rivers, streams, lakes and ponds are diverse and complex ecological systems. Theirpermanent biota is comprised of fish, amphibians, crayfish, mussels, worms, sponges, hydras,hydromorphic plants, mosses, algae, insects, diatoms and a large number of microscopic protistsadapted to life in freshwater. As with terrestrial species the patterns of species distributions occurat many scales and correspond both broad climatic and historic factors as well as very localfactors such as stream size and velocity, bottom substrate, water chemistry and dissolved oxygenconcentrations.The objective of the freshwater analysis was to identify the most intact and functional streamnetworks and aquatic lake/pond ecosystems in such a way as to represent the full variety offreshwater diversity present within an ecoregion.Geographic Framework for Aquatic AssessmentsPatterns of freshwater diversity corresponds most directly with major river systems and the largewatershed areas they drain. These drainage basins cut across the TNC Ecoregions that weredeveloped based on terrestrial processes. In order to assess freshwater systems we needed aseparate stratification framework of regions and drainage basins that made ecological sense foraquatic biodiversity patterns. To this end, we adopted an existing national map of freshwaterecoregions developed by the World Wildlife Fund 1 after Maxwell’s Fish ZoogeographicSubregions of North America. 2 Within each freshwater ecoregion, the Nature Conservancy’sFreshwater Initiative developed a further stratification level of Ecological Drainage Units. The* Olivero, A.P. (author) and M.G. Anderson, and S.L. Bernstein (editors). 2003. Planning methods for ecoregionaltargets: Freshwater aquatic ecosystems and networks. The Nature Conservancy, Conservation Science Support,Northeast & Caribbean Division, Boston, MA.The standard methodologies sections created for this and all Northeast ecoregional assessment reports were adaptedfrom material originally written by team leaders and other scientists and analysts who served on ecoregionalplanning teams in the Northeast and Mid-Atlantic regions. The sections have been reviewed by several planners andscientists within the Conservancy. Team leaders included Mark Anderson, Henry Barbour, Andrew Beers, SteveButtrick, Sara Davison, Jarel Hilton, Doug Samson, Elizabeth Thompson, Jim Thorne, and Robert Zaremba. ArleneOlivero was the primary author of freshwater aquatic methods. Mark Anderson substantially wrote or reworked allother methodologies sections. Susan Bernstein edited and compiled all sections.1 Abell et al. 2000.2 Maxwell et al. 1995REVISED 7/2003AQUA-1
Freshwater Ecoregions and Ecological Drainage Units together serves as an analog to theterrestrial ecoregions and subsections for the Northeast.Zoogeographic Subregions/Freshwater Ecoregions: describe continental patterns of freshwaterbiodiversity on the scale of 100,000-200,000 sq. miles. These units are distinguished by patternsof native fish distribution that are a result of large-scale geoclimatic processes and evolutionaryhistory. 3 For North America, we adopted the freshwater ecoregions developed by the WorldWildlife Fund. 4 Examples include the St. Lawrence Subregion, North Atlantic to Long IslandSound Subregion, Chesapeake Bay Subregion, and South Atlantic Subregion.Ecological Drainage Units (EDUs): delineate areas within a zoogeographic sub-region thatcorrespond roughly with large watersheds ranging from 3,000–10,000 square miles. Ecologicaldrainage units were developed by aggregating the watersheds of major tributaries (8 digit HUCs)that share a common zoogeographic history as well as local physiographic and climaticcharacteristics. These judgements were made by staff of TNC’s Freshwater Initiative afterconsidering USFS Fish Zoogeographic Subregions, USFS Ecoregions and Subsections, andmajor drainage divisions. 5 Ecological drainage units are likely to have a distinct set of freshwaterassemblages and habitats 6 associated with them. Depending on the amount of ecologicalvariation within them, some large river systems such as the Connecticut River were divided intomore than one EDU.Finer-Scale Classification of Aquatic Ecosystems and NetworksWithin the geographic framework of the zoogeographic subregions and ecological drainage unitsthere exits a large variety of stream and lake types. If you contrast equal sized streams, somedevelop deep confined channels in resistant bedrock and are primarily fed by overland flowwhile others are fed by groundwater and meander freely through valleys of deep surficialdeposits. Variation in the biota also exists as the stream grows in size from small headwaterstreams to large deep rivers near the mouth. We needed a way to systematically describe andassess the many types of stream networks and aquatic features that was both ecologicallymeaningful and possible to create and evaluate in an 18 month time frame. For these purposes,and in conjunction with the Freshwater Initiative, we developed a multiple scale biophysicalwatershed and stream reach classification within Ecological Drainage Units. This classificationframework is based on three key assumptions about patterns in freshwater biodiversity. 7• Aquatic communities exhibit distribution patterns that are predictable from the physicalstructure of aquatic ecosystems 8• Although aquatic habitats are continuous, we can make reasonable generalizations aboutdiscrete patterns in habitat use and boundaries distinguishing major transitions 9• By nesting small classification units (watersheds, stream reaches) within large climatic andphysiographic zones (EDUS, Freshwater Ecoregions), we can account for community3 Maxwell et al. 19954 Abell et al. 20005 Higgens et al. 20026 Bryer and Smith 20017 Higgins et al. 19988 Schlosser 1982; Tonn 1990; Hudson et al. 19929 Vannote et al. 1980; Schlosser 1982; Hudson et al. 1992REVISED 7/2003AQUA-2
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PLANNING METHODS FOR ECOREGIONAL TARGETS: FRESHWATERAQUATIC ECOSYSTEMS AND NETWORKS *IntroductionFreshwater biodiversity conservation is vital to The Nature Conservancy’s mission ofbiodiversity conservation. Compelling documentation of the perils facing freshwater biodiversityindicate that many of the most endangered species groups in the U.S. are dependent onfreshwater resources. Approximately 70% of freshwater mussels, 52% of crayfish, 42% ofamphibians and 40% of freshwater fish are classified as vulnerable or higher with respect toextinction risks. Additionally, water itself is a critical resource to terrestrial species andecosystems and its patterns of drainage and movement have shaped the larger landscape in theNortheast.Freshwater rivers, streams, lakes and ponds are diverse and complex ecological systems. Theirpermanent biota is comprised of fish, amphibians, crayfish, mussels, worms, sponges, hydras,hydromorphic <strong>plan</strong>ts, mosses, algae, insects, diatoms and a large number of microscopic protistsadapted to life in freshwater. As with terrestrial species the patterns of species distributions occurat many scales and correspond both broad climatic and historic factors as well as very localfactors such as stream size and velocity, bottom substrate, water chemistry and dissolved oxygenconcentrations.The objective of the freshwater analysis was to identify the most intact and functional streamnetworks and aquatic lake/pond ecosystems in such a way as to represent the full variety offreshwater diversity present within an ecoregion.Geographic Framework for Aquatic AssessmentsPatterns of freshwater diversity corresponds most directly with major river systems and the largewatershed areas they drain. These drainage basins cut across the TNC Ecoregions that weredeveloped based on terrestrial processes. In order to assess freshwater systems we needed aseparate stratification framework of regions and drainage basins that made ecological sense foraquatic biodiversity patterns. To this end, we adopted an existing national map of freshwaterecoregions developed by the World Wildlife Fund 1 after Maxwell’s Fish ZoogeographicSubregions of North America. 2 Within each freshwater ecoregion, the Nature Conservancy’sFreshwater Initiative developed a further stratification level of Ecological Drainage Units. The* Olivero, A.P. (author) and M.G. Anderson, and S.L. Bernstein (editors). 2003. Planning methods for <strong>ecoregional</strong>targets: Freshwater aquatic ecosystems and networks. The Nature Conservancy, <strong>Conservation</strong> Science Support,Northeast & Caribbean Division, Boston, MA.The standard methodologies sections created for this and all Northeast <strong>ecoregional</strong> assessment reports were adaptedfrom material originally written by team leaders and other scientists and analysts who served on <strong>ecoregional</strong><strong>plan</strong>ning teams in the Northeast and Mid-Atlantic regions. The sections have been reviewed by several <strong>plan</strong>ners andscientists within the Conservancy. Team leaders included Mark Anderson, Henry Barbour, Andrew Beers, SteveButtrick, Sara Davison, Jarel Hilton, Doug Samson, Elizabeth Thompson, Jim Thorne, and Robert Zaremba. ArleneOlivero was the primary author of freshwater aquatic methods. Mark Anderson substantially wrote or reworked allother methodologies sections. Susan Bernstein edited and compiled all sections.1 Abell et al. 2000.2 Maxwell et al. 1995REVISED 7/2003AQUA-1