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Biodiversity Sites Stream, Pond, Rivers, and Lakes Selection criteria for streams and rivers Table 2: "SuAsCo Biodiversity Sites" The purpose of identifying SuAsCo Biodiversity Sites is to establish, on a regional scale, which areas are important to protect and to manage for biodiversity. It is hoped that the Sites will serve as focal points for cooperative conservation efforts by the appropriate towns, land trusts, and state agencies so that each entity can use their limited resources to the best effect.
Selection of Biodiversity Sites The criteria for selecting Biodiversity Sites is based on current conservation biology science. These parameters are derived from several publications, white papers, and interviews with scientists and local authorities. Sites have been selected for biodiversity values only. Aesthetics, agricultural values, recreational use, and water supply protection were not considered, although in many cases Biodiversity Sites may contribute to them. In some cases, these other values are in conflict with biodiversity values. These issues will be addressed in the section on stewardship. Threats or feasibility of protection were not considered in the selection criteria. The intent of the list of SuAsCo Biodiversity Sites is to indicate what are the important sites for biodiversity and why, so that leaders and concerned citizens can make a clear choice as to their goals and then determine how to proceed. Overarching priorities • Areas on the Bio-map - to be determined by Natural Heritage June 2001 • Areas of Critical Environmental Concern (ACECs) • Large parcels with a mosaic of quality habitats, both upland and wetland • Large patches of quality community types • Small patches of quality, unusual community types which are well buffered.
Evaluation guideline • Size and configuration: Large parcels, preferably with a core of protected conservation land. Large, more or less circular, unfragmented parcels have less edge and more interior area to natural communities. Large areas tend to include more diversity within a matrix community type and often include other small patch communities. While forest parcels of over 1000 acres are preferable and feasible within the SuAsCo Watershed, adequate size varies according to community type or Focal Species. • Areas shown on MNHESP Atlas 2000-2001: Priority Habitat for Rare Species and Estimated Habitats for Rare Wildlife and Certified Vernal Pools; also exemplary natural community types. The inclusion of these sites in the SuAsCo Biodiversity Sites was based on the quality of the occurrence as recorded by Natural Heritage and the context of the site. All the coverages indicated by the NHESP Atlas should be given special consideration. • Connectivity: Sites that are adjacent to other protected sites enhance the value of both. Connections to resources beyond the watershed boundary, as well as within the watershed, are important. • Buffers/perimeters: Low density development, relatively small roads, and similar adjacent habitat protect and enhance the value of the core site. • Representation of different natural communities: Protection of good examples of different community types listed by the NHESP in their publication Natural Communities of Massachusetts. By representing different community types, the range of organisms from invisible mites to site specific birds will be protected (see Section II). • Viable populations or regular occurrences of focal species: Sites that are likely to or in fact do support viable populations of Focal Species or sites that regularly support healthy individuals of Focal Species so that these individuals contribute to viable populations. • Linkages/corridors: Linkages along wetlands and streams or vegetated wildlife corridors that can be protected and managed for wildlife (see below). • Natural disturbance dynamics: Areas where natural dynamics of forest succession, flooding, and beaver activity are able to continue without undue interference by people. • Minimal exotic species: Areas with minimal invasion of invasive exotic species or where exotics are manageable with readily available resources. • Good examples or unusual combinations of geological features: Intact drumlins, eskers, glacial moraines, kame terraces, or riverine bluffs feature different soil types, topography, and hydrology that contribute to formation of different natural communities. • Topographic variability: Topographical variability has been shown to increase native biodiversity. • Human disturbance: In general, sites with less human disturbance are better than disturbed sites. The latter include invasions by exotic species, recent forest cuttings, hydrological alterations (including ditching, damming, filling, discharges, and water withdrawals), topographical changes (grading or excavation), soil disturbances, etc. There are exceptions to this criterion. Grasslands, successional fields, and wildlife management areas, such as Great Meadows impoundments, provide habitat for certain Focal Species. In some cases reservoirs, utility corridors, and aqueducts may be important. It is understood that virtually all our landscape has been influenced by human activity in the past to some degree or another. • Permanently protected conservation land: Already protected lands owned and managed by federal and state agencies, municipalities, or non-profit organizations with a conservation mandate are particularly good core areas. • Defensible from detrimental disturbance: Areas that are defensible from encroachments or detrimental disturbance in the future, such as lands with conservation restrictions (CRs), agricultural preservation restrictions (APRs), or public water supplies. • Organizational capacity: Areas where management of habitats, including restoration, can be done with minimal inputs over the long-term and the ownership entity has the mandate and/or capacity to manage for natural biodiversity. • Distribution: When possible, community types should be represented throughout the watershed to provide biodiversity reserves in different locations and to reduce risk of loss by localized stochastic events such as disease outbreaks, windstorms, and fire. Process for site selection Sites were selected using the guidelines above and incorporating the best professional judgment. The specific steps for site selection are listed below. 1. Review of data - When available, the following background information was used to determine sites: USGS topographical maps, black-and-white and color infra-red aerial photos, USDA soil maps, USGS geology maps, NHESP information on rare and endangered species, water quality reports by Massachusetts Department of Environmental Protection/Division of Watershed Management; MassGIS information, including wetland and stream layers; and inventories and management plans of national wildlife refuges, Sudbury Valley Trustees properties, and state parks. (see references for a complete list). 2. Review of Open Space Plans - Many towns have produced recent open space plans which indicate areas of conservation interest. The plans also provide helpful information on geology, soils, plant communities, and corridors. Plans with specific descriptions of the plant communities and wildlife found on conservation properties were most helpful. 3. Consultation with biologists, land managers, and local experts - Conservation commissions were notified of the project by mail or phone. Conservation commissioners or agents often were the main source of information, but local hunters, trackers, botanists, birders, and land trust volunteers were contacted, too. These on-the-ground people were essential to the process. Unfortunately, given the time of year, many individuals were not available. Also, there was little time to follow up on many of the recommended leads. 4. Site visits and follow-up conversations - All sites were visited by the author, but several of these only briefly, usually 2-3 hours. In a few cases, review was conducted by driving by the area. In such cases, every effort was made to talk with someone familiar with the site. Not surprisingly, some areas require more investigation. 5. Outlining of sites - Biodiversity Sites were delineated on USGS topographical maps. As large an unfragmented area as possible was included to reduce edge or to buffer sensitive community types. Usually, roads or development determined the actual line. The intention was to be more inclusive than exclusive. 6. Review by SuAsCo Biodiversity Plan Advisory Committee - All sites were reviewed by the Advisory Committee. 7. Documentation of rationale - The final process of citing values for each site was the ultimate test for inclusion. In some cases more information is the main recommendation. Biases: Several biases affected what was included as SuAsCo Biodiversity Sites. Some towns had more complete information to work with. Concord, for instance, has not only a very useful open space plan, but also an active community of naturalists; therefore, small areas of regional significance were determined. These relatively small-patch areas serve as examples to other towns of the value of conducting in-depth biodiversity surveys. Bird habitats and herp (amphibian and reptile) habitats were often included because of regional expertise and interest. Bird watching is a popular pastime, and there are many expert birders in the SuAsCo who have maintained Christmas Bird Count records and other lists for over fifty years. The high profile of vernal pools and public appeal of turtles and salamanders have resulted in good information about their locations. Records in the Natural Heritage data base are likely biased to the areas east of I-495, again due to the level of naturalist interest. Information on the eastern half of the watershed is also greatest because of the author’s professional connections and her having conducted previously several inventories in the area. Streams, Rivers, Ponds and Lakes
Streams, rivers, ponds, and lakes are not specified as SuAsCo Biodiversity Sites in this report because the information to assess these communities is limited. First, The Natural Heritage Program has not compiled descriptions for aquatic communities as it done for upland and wetland natural communities. Information on assessment criteria of streams for biodiversity purposes -- meaning the integrity of natural stream systems --other than as trout habitat is very limited. Some information was helpful, such as fish stocking information compiled by the Division of Fisheries and Wildlife and water quality testing conducted by Massachusetts Division of Watershed Management to assess reference streams. However, overall there is limited consistent coverage of the entire watershed. Consequently, there is no data to evaluate the relative importance of each stream in the SuAsCo Watershed to determine biodiversity priorities. Therefore, the Advisory Committee decided to include streams, lakes, and ponds only when the adjacent natural communities were considered to be of value. These assessment difficulties having been stated, it is clear that streams are key components to the health of the watershed. Streams provide habitat for water-dependent organisms which in turn are important for upland species: mayfly larvae for trout and breeding birds, crayfish for raccoons and mink, and sunfish for herons, kingfishers, and osprey. It is important that wildlife such as otter --as well as people--are not threatened by bioaccumulations of toxins. Furthermore, wetland communities, such as red maple swamps, shrub swamps, and marshes, are often directly connected to streams and rivers. These natural communities are enriched by the flowing waters. Upland forests with streams and ponds support increased biodiversity as well. In turn, intact natural communities help protect streams, rivers, and ponds by reducing sediment, nutrient, and pollutant runoff and by providing shade and structure. Different types of plants provide critical combinations and amounts of nutrients for stream life--up to 90% of the total. Surrounding uplands provide habitat for water dependent species, such as turtles and toads. Finally, streams are vital corridors for both terrestrial and aquatic organisms. Protection of streams and other water resources is vital to biodiversity. It doesn’t require much research to know that our streams are in jeopardy. Not one is entirely free flowing. Most have been dammed, many have been ditched, and all go through culverts under roads. Initially free flowing with ample buffers, the first and second order, cool-water streams found in the western part of the watershed all drain under I-495. Cross roads, even highway cloverleaves, segment trout streams such as Cold Harbor and Great Brooks. The rest of their run is constrained and restricted. Roads run parallel for miles next to streams such as Nashoba Brook, subjecting them to salt, pollution, and hazardous waste impacts. Warm-water streams in the eastern portion of the watershed are hemmed in by development and are being overwhelmed by purple loosestrife. Exotic species invade as a result of culvert repairs, salt runoff, and exposure to repeated introductions of seeds from passing vehicles. The mainstems of the Assabet, Sudbury, and Concord rivers are loaded with sediments, nutrients, and pollutants. As a result of such disturbances, exotic aquatic invasives, such as water chestnut and curly-leaved pondweed, clog channels. Carp constantly stir the waters. Wastewater treatment plants discharge into the rivers and water is being withdrawn for drinking water supplies directly in Billerica and indirectly by municipal wells adjacent to mainstem rivers and tributaries. The water quality and quantity of the many tributaries and mainstem rivers of the SuAsCo Watershed are severely compromised. Despite these impacts, there are sections of streams rich with diversity. Least bitterns, native trout, wood turtles, river otters, and rare dragonflies still live in our waterways. Native alewives are being reintroduced. Twenty-nine miles of the mainstems of the Assabet, Sudbury, and Concord rivers have been designated as Wild and Scenic Rivers because they have nationally significant resources. Indeed, the mainstem rivers, despite the accumulation of years of human disturbances, are perhaps the most significant resource in the watershed. Cleaning up their upstream sources would significantly improve this habitat. How municipalities, industries, business owners, and homeowners treat the rivers and streams determines the quality of biodiversity throughout the SuAsCo Watershed. While this report has not highlighted specific streams per se, the following guidelines for determining potentially significant streams, or portions of streams, are given below. It is hoped that the guidelines will encourage additional protection and comprehensive restoration measures. Along any stream, the Wetlands Protection Act regulations, which incorporate the Rivers Protection Act, should be strictly enforced and other programs, such as Riverway’s Adopt-A-Stream Program, should be utilized to improve these vital resources. Additional water quality/quantity data collection should be supported. We need to sustain what we have left and work to increase the native diversity by protecting the least compromised habitats and working to restore the system as a whole. Fortunately, the many watershed organizations and the SuAsCo Watershed Community Council Task Forces, are already working on these goals.
Selection criteria for streams and rivers The following are general criteria for selecting streams and rivers for biodiversity. They are based in large part on the assumption that streams whose physiological and hydrological features are intact are more likely to retain some biological integrity and are easier to restore than highly degraded streams: A. Overall: 1. Natural hydrological processes relatively intact - this is the key to preserving the biological diversity of any ecological system. 2. Reference streams of DEP. 3. Minimum development around the headwaters - preferably the headwaters are completely protected by large buffer zones of natural vegetation >300 feet wide. 4. Connectivity of headwaters to lower portions of tributaries. 5. Wide, naturally vegetated buffers ( >300’-500’) along extensive stretches of stream >1000 feet long to buffer non-point source pollution and provide an adequate wildlife corridor. 6. Minimal point sources of pollution. 7. Naturally flowing channels vs. straightened channels. The more sinuous the channel the greater the opportunity for nutrient uptake, flood attenuation, and habitat creation. 8. Minimum impoundments as these create pond conditions and interrupt the movement of river-dependent organisms. 9. Minimum road crossings or culverts. Where culverts are present, they should be engineered to allow for migration of fish and other wildlife in and along the stream. 10. Roads do not run closely parallel to the stream for any significant length. 11. Substantial sections of stream are already protected for conservation purposes. 12. Diversity of stream types, i.e., warm water, cool water, high gradient , low gradient. 13. Distribution of protected streams throughout the watershed, i.e., tributaries to different parts of Assabet, Concord, and Sudbury, so they can serve as reservoirs of biodiversity when nearby streams are restored.
B. Cold water streams: Primarily found in the western portion of the watershed. 1. Streams which provide habitat for native eastern brook trout. 2. Streams that are stocked with trout. These sites usually support trout for some period of time due to water quality and temperature; however, many of the trout are fished out, and/or are unable to survive summer or winter temperature extremes. 3. Representation of streams with different substrates - sandy, gravely, rocky bottom, bedrock. 4. Higher gradient streams. 5. Spring-fed streams - these are less likely to dry out in summer. 6. Observation of Focal Species and/or rare species.
C. Warm water streams of low gradient: typically in eastern portion of watershed. These streams often will support similar generalist species throughout the riverine system, including fish, frogs, and turtles. 1. Support fluvial specialists (eastern brook trout, longnose, shortnose dace) vs. pond fish (catfish, carp, bass, perch, bullhead). 2. Adjacent to significant wetlands or forests. 3. Diversity of adjacent habitat types so as to provide a variety of habitats for different species. 4. Recent records/observations of focal or rare species.
It is strongly recommended that the state agencies and watershed groups work together to conduct a more comprehensive study of riparian and stream biodiversity values in the SuAsCo Watershed. This includes using benthic macroinvertebrate sampling. The need is to protect and restore the natural diversity of streams, not just drinking water quality or recreational values, in the SuAsCo Watershed.
The long-term viability of biodiversity on even large areas of conservation land depends on linkages to other areas. In fragmented landscapes linkages between conserved areas are tenuous. While wildlife corridors are touted as key, actual criteria for viable corridors is still in the research stage. Different organisms move to different places at different times, along different pathways, for different purposes. A turtle has a different route than a coyote. It is unclear how bear and moose cross I-495. It also is not known how compatible different users are: will the fox and the hare use the same travel route? Also, it is important to note that human uses can be in conflict with animals trying to use the same area. In any case, the best scientific advice recommends planning routes for animals to move from place to place safely. Corridor criteria For the purposes of this plan, corridors were determined by: 1. Adjacent or nearby protected open space that connects larger parcels. 2. Stream corridors, preferably with adjacent upland habitat and minimal culverts. 3. Broad areas with abundant cover vs. narrow areas with lack of cover. 3. Small, two-lane roads with local traffic vs. two-lane or larger routes with commuter or commercial traffic. Highways such as I-495 are considered blocks unless there is a documented pathway through large culverts, overpasses, or underpass. 4. Low density, “low impact” development vs. dense commercial development. Neighborhoods with small 1950s-size houses on wooded 1-2 acre lots are more hospitable than new luxury homes surrounded by extensive lawns. 5. Vegetated utility corridors and old railroad tracks probably provide relatively safer passage for larger mammals than mowed aqueducts. 6. The extensive MDC reservoir system, while not providing the best habitat, probably provides safe passage for many wide-ranging species. Ideally, inventory and tracking of animals and an assessment of road crossings and road kill would provide information on the best routes. In practice, this plan depends on MassGIS data and town open space plans to determine best corridors. Corridors will require careful stewardship if they are to be of value. This issue will be addressed in the stewardship section. The following information is provided in this report to highlight the sites: -- Watershed maps with Biodiversity Sites and Corridors -- Table of Biodiversity Site descriptions -- Maps of individual Biodiversity Sites based on USGS maps. Watershed maps SuAsCo Watershed Biodiversity Sites illustrates the combination of the sites and corridors in the watershed. It is a MassGIS “layer” overlying other MassGIS information layers that include roads, streams and wetlands, town lines, and the watershed outline. SuAsCo Watershed Biodiversity Sites and Natural Heritage Program Habitats illustrates the SuAsCo Biodiversity Sites in relation to other Natural Heritage sites represented in their 2000 Atlas. Not all Natural Heritage sites are contained within the “polygons.” However, all Natural Heritage sites should be considered important to preserving biodiversity in the watershed. Corridors are represented by arrows. In some cases they may represent a very precise route, such as through a heavily developed city, while in other cases the options are broader, such as through lightly developed neighborhoods. Only the most important linkages are indicated. Some areas adjacent to Biodiversity Sites are delineated as “connectors.” While not necessarily representing natural communities or Focal Species habitat, these connectors significantly enhance the value of the adjacent Biodiversity Sites. The type and density of development within these connectors should be carefully assessed. Site descriptions Site descriptions are provided for individual sites and are arranged in clusters based on geographical areas. The information is organized as follows:
Site maps SuAsCo Biodiversity Sites are represented by “polygons,” a method utilized by the Massachusetts Natural Heritage Program in delineating areas of concern. For this report, every effort was made not to include areas of dense development; however, scattered houses and small roads may be included, as in most cases they should not affect the conservation value of the sites. Even so, polygon outlines should be considered as general indicators of the area of the site. USGS topographical maps are used as base maps on the individual sites maps because they reveal helpful information: street and other location names, topography, streams, and development features. They do not show the extent of natural communities. The latest maps are dated 1989 and may not represent recent development. The actual outline was based on the most current black-and white aerial photos available from GIS and site visits. Even so, recent developments may be included inside the polygon. Indeed, several of these sites are under imminent threat of development and may in fact be lost by the time this report is circulated. Note: In Contrast to Heritage Program Priority Sites, Estimated Habitats, and Certified Vernal Pools, SuAsCo Biodiversity Sites per se do not have any legal standing whatsoever
Table 2: "SuAsCo Biodiversity Sites" |