Chapter 4: Corridor Benefits

Natural Resources Conservation Service (NRCS)

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· ENVIRONMENTAL BENEFITS

· SOCIAL BENEFITS

· ECONOMIC BENEFITS

INTRODUCTIONAs habitats continue to be lost to various types ofdevelopment and landscapes are increasinglyfragmented, land managers are relying on theecological functions of corridors to conserve soil, water,fish and wildlife. Conservation of these basic resourcesprovides benefits for individual landowners and thelarger community. The benefits associated withcorridors can be grouped into three categories:

The last section of this chapter discusses the potentialadverse impacts that also can be associated withcorridors.

ENVIRONMENTAL BENEFITSThe environmental benefits of corridors come fromthose functions that improve the condition of thewatershed. Two general kinds of environmentalbenefits are provided by corridors:

Environmental Services· Reduced flooding

· Reduced soil erosion

· Improved water quality

· Increased water quantity

· Groundwater recharge

· Bank stabilization

· Improved air quality

Habitat

· Terrestrial

· Aquatic

ENVIRONMENTAL SERVICES

Stream/riparian corridors and attendant wetlands infloodplains provide floodwater storage, desynchronizeflood flows and slow flood velocities. Downstreamflooding and the potential for flood damage arediminished when floodwater volume and velocity arereduced. Stream banks stabilized by the roots ofriparian vegetation reduce bank erosion, a major sourceof sedimentation in some streams.

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Stream corridors also function as sponges retainingsoil moisture, and in some locations rechargingground water supplies. Water stored in soil isreleased slowly back into rivers and streams, whichhelps maintain stream flows and sustain aquaticlife during dry seasons.

During the growing season, healthy riparianvegetation intercepts most of the sediments andagricultural chemicals in sheet and shallowsubsurface flow originating in fields and pasturesbefore they can reach streams or rivers. This filterfunction of riparian buffers protects many wetlands,lakes, and streams at a critical time when they arenutrient stressed and prone to eutrophication. Inthe fall some of the nutrients produced in ripariancorridors are released when leaves, grass, needlesand limbs fall or are washed into streams and rivers.This cycling of nutrients supplies the food energyrequired to support diverse populations of aquaticorganisms throughout the stream system. Forestedstream corridors are also an extremely importantsource of woody debris for fish habitat, bankarmouring, and as natural grade control structures(Figure 4-1).

Continuously vegetated riparian corridors are moreeffective at maintaining both surface and subsurfacewater quality than those that are discontinuous. Waterquality is strongly influenced by water temperature.A slight increase in water temperatures above 59o Fwill produce a substantial increase in the release ofsedimentary phosphorus, which can result ineutrophication. Thus, a leafy canopy provided by woodyriparian vegetation can reduce the adverse affects ofpollutants. In addition, cool water, which has a higheroxygen content, is necessary to support populationsof many game fish, particularly trout and salmon. Acool, moist microclimate, is also a requisite for manyterrestrial species. For a more detailed discussion ofthe environmental services provided by stream/ripariancorridors, see Stream Corridor Restoration: Principles,Processes, and Practices (www.usda.gov/stream_restoration).

Introduced upland conservation corridors are usuallydesigned to function as barriers, filters and sinks. Theyreduce soil erosion caused by wind and water,conserve soil moisture, trap sediments and absorbagricultural chemicals. Shelterbelts reduce windvelocity for a distance of 8 to 10 times their height onthe lee side.

When wind velocity is diminished it has less energyto dry out soil and plants and to dislodge and transportsoil particles. Continuous windbreaks eliminate theproblem of airflow through gaps or around the ends ofwindbreaks which can significantly diminish theireffectiveness. A continuous windbreak or remnantcorridor is also more effective at capturing and retainingsnow in the field. Captured snow can represent over20% of the annual soil moisture in north centralagricultural areas (Figure 4-2).

Researchers report field barriers of tall wheat grassreduce potential wind erosion to nearly 7% of openfield erosion. When the volume of airborne soil particlesin the watershed is reduced, air quality is enhanced.

Windbreaks, buffer strips, field borders, grassedwaterways, and roadsides, like riparian corridors, areeffective sediment traps and nutrient sinks. Anestimated 95% of sediments from row crop fields weretrapped in grassed waterways in an Iowa study area.In Illinois, grassed waterways and forest buffersreduced nitrates in subsurface water an estimated80 to 90%. Corridor vegetation can, however, beoverwhelmed by sediments and chemicals andabsorption capabilities may be reduced significantly.

Figure 4-1 Cross section of a windbreak

Figure 4-1: The woody debris in this stream channel provides criticalhabitat for native trout and dampens erosion of the stream bank.

Figure 4-2: This windbreak captures snow which increasessoil moisture in adjacent fields and provides critical winterwildlife habitat.

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ENVIRONMENTAL SERVICES: VALUE-ADDED BENEFITS OF CONNECTIVITY

A linked system of various conservation corridor typesproperly sited will optimize soil and water conservationin the watershed by:

· Increasing efficiencies

· Integrating ecological functions

When terraces, filter strips and other conservationmanagement practices are linked to grassedwaterways and riparian buffers, the value-addedbenefits include longer concentration times for overlandwater flows, increased infiltration, and increasedretention time, which facilitates assimilation ofnutrients.

Systems of upland corridors can make a significantcontribution in reducing flood water volume,sedimentation, and pollutants in adjacent receivingstreams. The Nutrient and Sediment Control Systemdeveloped by the NRCS in Maine combines sedimentbasins, filter strips, constructed wetlands, and deepponds into a single, connected system that has a90% removal rate for sediment and phosphorus, evenafter extreme storm events.

HABITAT

Habitat is defined here as the ecosystem in which aspecies lives. Each species responds differently tophysical variables in the ecosystem including thepattern of patches, corridors, and matrix. Forexample, wildlife differ in their ability to disperse. Somespecies like reptiles have physical limitations, othershave behavioral or physiological limitations. Mostspecies are not limited in their ability to use corridorsbut experience high levels of mortality dispersingacross landscapes that do not have corridors.

Many species instinctively seek patterns, which meettheir needs for food, cover, water, space, reproduction,and security; others learn this information (Figure 4-3). The high edge to interior ratio of most corridorsmakes them particularly attractive to edge habitatspecies. However, because corridors often do not

provide all the requisiteresources, the homerange of many speciesextends beyond thecorridor into adjacentpatches and the matrix.

· Type of vegetation in the corridor

· Type of vegetation adjacent to the corridor

· Surrounding land uses

· Corridor management

· Geographic location

Many wildlife species in agricultural landscapes haveadapted to wooded corridors and expanded theirrange. Others that require large patches of forest orprairie have been displaced. The habitat value of cor-ridors in highly fragmented landscapes is well docu-mented. Riparian corridors, shelterbelts windbreaks,and roadsides have been extensively researched. Lessresearch has been done on the habitat value of fieldbuffer strips, grassed waterways, conservation ter-races, powerline and other introduced corridors.

Stream/Riparian Habitat

Stream corridors are among the most productivehabitats in all regions of the country. They areparticularly important in arid and semi-aridlandscapes. The vegetation in most riparian zones isstructurally more diverse and biomass production ishigher than the adjacent matrix providing an increaseddiversity of niches for wildlife to exploit. In addition,water, aquatic insects, and fish provide resourcessupporting wildlife species that require both aquaticand upland environments.

Wildlife species diversity and density are high in ri-parian zones. In a Blue Mountain study area in east-ern Oregon, 75% of the terrestrial vertebrates weredependent upon or preferred riparian habitat. Biolo-gists Stauffer and Best estimated an average of 500breeding pairs of birds per 100 acres in riparian corri-dors in Iowa compared to 340 pairs in upland forests.Bird densities in riparian zones in Arizona were 66%higher than densities in the adjacent desert upland(Figure 4-4). Riparian corridors are also important

travel lanes for manyspecies. They may beimportant for dispersalas well as movementwithin species homeranges.

Figure 4-3: Many largemammals use traditionalmigration corridors betweensummer and winter range.

Figure 4-4: Many birdsnative to Arizona like thiscardinal rely on riparianhabitats for food and cover.C

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Researchers studying roadsides found several factorsaffected corridor use by wildlife:

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Windbreaksand Shelterbelts

The diversity of eco-logical niches andweather protectionafforded wildlife bywindbreaks are par-ticularly important inagriculturally domi-nated landscapes.Windbreaks providefood, nesting, brood-ing, loafing, thermal,and escape cover for

many species of birds and mammals (Figure 4-5).They are also used as travel lanes by both migratoryand nonmigratory species. Windbreaks are importantresting stops for songbirds during spring and fallmigration. At least 108 species of birds are known touse shelterbelts for foraging, nesting, or resting.

In seven Minnesota windbreaks, a mean nest densityof 36 nests per acre was reported. ResearcherShalaway reported higher nest success for low andmid-level nesting species in fencerows than in nativeshrub or woodlands.

Windbreaks are an important habitat component formany game species including: the ring-neck pheasant(Phasianus ciolchicus), northern bobwhite (Colinusvirginianus), mourning dove (Zenaida macroura), wildturkey (Meleagris spp.), eastern cottontail rabbit(Sylvilagus floridanus), western cottontail rabbit(Sylvilagus audubonii), gray squirrel (Sciuruscarolinensis), fox squirrel (Sciurus niger), and whitetaildeer (Odocoileus virginianus). Windbreaks andremnant wooded corridors are used as travel lanes bycarnivores like the gray fox (Urocyon cinereoargenteus)and other mid-sized predators.

Grassed Waterways and Buffer Strips

Grassed waterways and in-field buffer strips aretypically seeded in a monoculture of exotic grassesand share similar locations embedded in theagricultural matrix (Figure 4-6). However, they areimportant habitats for many ground nesting speciesand species that prefer early successional vegetation.Fourteen bird species were observed nesting in grassedwaterways in one Iowa study. Nest densities of over1,100 nests per 250 acres of grassed waterways werereported. These nest densities exceed densities foundin no-till and cropped fields. Dickcissels (Spizaamericana) daily survival rates when nesting ingrassed waterways were the same as those reportedfor old fields and prairie remnants. Researcherssuggest grassed waterway habitats could be evenmore productive if seeded with a mix of native grassesand forbs.

Other Corridors

Roadsides and fieldborders also sharecommon locationaland structural char-acteristics. Althoughexceptions exist,they are typically onthe edges of theagricultural matrix and

are dominated by a few grass species. However,biologists working in Minnesota report that roadsidessupport over 300 species of plants and wildlifeincluding some of the last remnant populations ofnative grass and forb species in the state.

Wildlife biologists have extensively researched thevalue of roadsides as habitat for wildlife, particularlygame species (Figure 4-7). In intensively farmedlandscapes, roadsides are a particularly importanthabitat component for ring-neck pheasants, graypartridge, cottontail rabbits, and a number of songbirds.Researcher Lars Anderson reported 27 species of birdsusing Utah roadsides from April to November; 12 ofthese species are known to nest in roadsides.Researchers reported relatively high levels of birdspecies richness in upper Midwest roadsides. Anestimated 27% of the pheasants recruited into the fallpopulation in Minnesota were produced in roadsides.Although losses to predation and parasitism forpheasants and songbirds nesting in roadsides arerelatively high, they generally do not exceed those ofthe matrix.

Figure 4-6: This unmowed grassed waterway offers habitatfor ground dwelling bird species.

Figure 4-5: Generations ofwoodpeckers, flickers, andbluebirds have been reared in thiswindbreak snag.

Figure 4-7: Pheasants are aprimary beneficiary of qualityroadside habitat.

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WILDLIFE HABITAT: VALUE-ADDED

BENEFITS OF CONNECTIVITY

Biologist Reed Noss notes that two effective ways toimprove habitat quality while mitigating the effects offragmentation are to increase effective habitat areaand connectivity. Conservation corridors are one toolthat can do both. In our highly fragmented landscapes,the value of connecting habitats far outweighs thepotential disadvantages. Some of the potential value-added benefits of connecting patches withconservation corridors for wildlife include:

· Increased habitat area

· Increased opportunities for colonization

· Habitat accessibility

· Increased niche diversity

· Escape cover

Increased Habitat Area

Perhaps the most significant benefit of conservationcorridors in urban or agriculturally dominatedlandscapes is increased habitat area. For instance, acontinuous 30-foot wide windbreak that surrounds aquarter section of agricultural land can add over 3-1/2acres of valuable wooded habitat. As Noss pointsout: �corridors, even narrow ones, provide habitat inwhich some kinds of organisms will live and reproduce.�

Additional habitat benefits can be realized if corridorwidth is increased (Figure 4-8). Wider corridorsobviously increase total area but they also provide forthe life requirements for a greater diversity of species.In addition, wider corridors if properly designed maymitigate some of the negative effects of edge andcontain some forest interior habitat.

Figure 4-8: The lower end of this riparian corridor is wide enough toprovide habitat for interior dwelling species.

Increased Opportunities for Colonization

Properly located conservation corridors that connectwith each other and adjacent patches may facilitateimmigration and colonization of habitat patches withinthe watershed. Researchers studying white-footedmice (Peromyscus leucopus) in Ontario found that anetwork of corridors which connected shelterbelts towoodlots was beneficial for recolonization of vacantpatches.

Corridors designed to meet the specific requirementsof species vulnerable to local extinction can reducetheir risk. Immigration may help sustain localpopulations and connected patches may facilitaterecolonization of areas within the local speciesextinction.

When a network of several alternative corridors or�stepping stone� patches are provided within thelandscape, additional value-added benefits may beachieved (Figure 4-9). A redundant network mayincrease dispersal opportunities in the event that one

or more of the corridors areblocked, severed, or madetemporally dysfunctional bydisturbance such as fire,drought, or insect outbreaks.

Figure 4-9: Parallel windbreaks inthis Missouri landscape providewildlife alternative routes from uplandpatches to the riparian corridor.

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Habitat Accessibility

Corridors connecting patchesincrease overall habitat qualitywithin the watershed. Theyprovide wildlife relatively safeaccess to a diversity of habitatresources, which are typicallydispersed across thelandscape and may changewith climate and seasons.Corridors facilitate dispersalamong subpopulationsincreasing the growth rate andstability of these populationsthrough recruitment andcolonization. Researchersfound corridors that connecteddrainageways to ridgessupported greater speciesrichness and abundance thancorridors limited to a singletopographic setting (Figure 4-10). Introduced corridorsaligned perpendicular tostream corridors facilitate wildlife migration fromuplands to riparian areas and wetlands during timesof drought. When corridors are aligned with naturalwildlife travel patterns, movement and access todifferent habitats are greatly enhanced; for wide-ranging species, effective foraging area also may beincreased.

Increased Niche Diversity

Connected landscapes can facilitate natural ecologicalfunctioning, which in turn may increase niche diversity.Connectivity, perpendicular to the long axis of a corridor(lateral connectivity), can be as important asconnectivity along the long axis.

Figure 4-11: Diverse vegetation types, heights, and spacing make this corridora rich habitat for many species.

Natural flooding, channel meandering, scouring, andsediment deposition all require lateral connectivity.Natural flooding, which creates conditions for plantsuccession, can reset forest stand age diversity andincrease the diversity of niches. Indeed, some specieslike the least bell�s vireo (Vireo bellii pusillus) are highlydependent on the 3 to 5 year old riparian vegetationfostered by periodic flooding. Increased niche diversitymay also increase wildlife species richness. BiologistSchroeder and others found breeding bird speciesrichness increased in shelterbelts as nichediversification was improved by the addition of snagsand increased foliage height diversity (Figure 4-11).The same is true for bats.

Escape Cover

Generalist carnivores and omnivores appear tobenefit from fragmented landscapes and maybe a strong factor in the decline of prey speciesin agricultural landscapes. Corridorsconnecting patches may bring prey/predatorrelationships into a better balance by allowingprey species more options to move with greatersafety among patches.

Figure 4-10: This network of interconnected riparian and upland corridors will provide forgreater wildlife diversity in this agricultural landscape.

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SOCIAL BENEFITSPerhaps the most important social benefits are theenvironmental services corridors provide. After all,clear air, an adequate supply of clean water, andproductive farm, forest and range lands are essentialto all life including humans. Other significant socialbenefits that corridors provide include:

RECREATION

Outdoor recreation has always been a significant partof American social life. In today�s fitness conscioussociety, demands for outdoor recreation are increasing.Much of the demand has focused on the recreationopportunities corridors afford. The linear configurationof corridors makes them well suited for a variety ofrecreational activities, especially trail oriented sports.Trails provide a venue for:

· Hiking

· Walking

· Jogging

· In-line skating

· Cycling

· Cross-country skiing

· Horseback riding

· Nature photography

· Wildlife viewing

Figure 4-12: Walkers enjoy a cool spring afternoon in anurban greenway.

Riparian corridors are especially attractive locationsfor trails (Figure 4-12). The presence of water, diversevegetation, moderated climate, and abundant wildlifeenhances the recreation trail experience. Boating,rafting, kayaking, tubing, fishing, and hunting arepopular non-trail activities in many corridors withperennial flowing water. Some riparian corridors havebecome so popular that demand frequently exceedsthe social and ecological carrying capacity. Socialconflicts between different types of users anddegradation of the riparian resource often result.

Other types of corridors are used extensively byrecreationists. The highly successful Rails-to-Trailsprogram has converted thousands of miles ofabandoned railroad ROWs into recreational trails. Anexcellent example is the 12-mile trail along the WoodRiver between Hailey and Ketchum, Idaho, used bycommuters as well as recreational cyclists.

Shelterbelts, field borders, grassed waterways, canals,and other types of strip corridors become importantrecreational resources during the hunting season(Figure 4-13). Pheasant and quail hunters appear tobe more successful in areas with shelterbelts andother types of woody cover. Research findings indicateKansas hunters spent an average of 40% of theirhunting time in or near shelterbelts, more than 80%spent at least some time hunting in shelterbelts duringthe season. These figures are particularly impressivegiven the small percentage of the Kansas landscapedevoted to shelterbelts.

Figure 4-13: Three good friends enjoy a hunt in quality habitat.

· Recreation

· Education

· Aesthetics

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One of the value-added benefits of corridor connectedlandscapes for recreationists is the continuity ofexperience that connectivity provides. Hunters preferto hunt in loops to and from the point where the huntbegins allowing continual hunting in promising habitat.A system of connected corridors and patches providesthis opportunity. When rivers and streams are free ofobstructions like culverts, dams, or diversions, waterrelated recreationists can kayak, tube, and fish withouthaving to continually get in and out of the water. Inboth cases, recreationists are free to concentrate ontheir recreational pursuit in an environment that addsrichness to the experience.

A safe corridor can reinforce recreational experiences.Continuously linked corridors with trails are safer thancorridors crossed by roads or railroads, pastures,fields or fences. The City of Boulder, Colorado installedexpensive trail underpasses at all road crossings alongBoulder Creek to minimize risks for recreationists. Ifroad crossings and other barriers are minimized, costlyretrofits can be avoided later.

EDUCATION

Rich in species diversity and typically accessibleremnant, riparian, and regenerated corridors are ideallysuited to outdoor education. Trails in corridors lendthemselves to a variety of formal and self-guidedinterpretative nature programs and educationalexperiences including:

· Natural history· Taxonomy· Archeology· History· Environmental science· Experimental design· The arts

Figure 4-14: The fish and aquatic insects caught by theseyoungsters will be the basis for a class discussion on theaquatic food chain.

· Continuity of experience

· Safety

RECREATION: VALUE-ADDED BENEFITS OF

CONNECTIVITY

Increasing numbers of science teachers are takingtheir classes outdoors, often into corridors to collectspecimens and conduct experiments (Figure 4-14).They have discovered that students learn more andretain concepts longer when involved in hands-oneducational experience.

Perhaps more importantly, corridors affordopportunities to investigate nature on your own. Harvardhistorian John Stilgoe noted a strong correlationbetween adults with a strong environmental ethic andthe opportunities they had at an early age to explorenature. Researchers Black and others found peopleliving near riparian corridors were more knowledgeableabout wildlife than those living only a few blocks away.The lessons learned in corridors may be extremelyimportant in molding future generations ofconservationists.

Archeological and cultural sites are often concentratedin riparian corridors. The juxtaposition of cultural andnatural resources presents exciting opportunities tointerpret the role societies past and present haveplayed in the evolution of a landscape. These sitesare also well suited to illustrating the importance ofcorridors in maintaining landscape health, stability andquality of life.

Some corridors are a valuable resource for research.National Resource Council researchers argue thatecologically stable stretches of riparian corridorsshould be preserved as research referencebenchmarks. At a smaller scale, remnant plantcommunities and wildlife populations are occasionallyfound in roadsides, railroad ROWs and other types ofcorridors. They are a valuable source of informationabout the ecology of native plant communities.Remnant plants may also be a source of regionallyadapted seed for restoration experiments and projectswithin a watershed.

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EDUCATION VALUE-ADDED BENEFITS OF

CONNECTIVITY

AESTHETICS

Visual resources that define a landscape�s aestheticquality are the lines, forms, spaces, colors, andtextures experienced from where people live, work,recreate, and travel. The quality of visual resourcesis important to those who reside in and travel througha landscape. Wooded corridors are often the mostsignificant visual lines, forms and space definingstructures in the landscape. Wooded corridors provide:

Figure 4-15: A view from this trail helps the observer understand that agricultureand the natural landscape can co-exist in harmony.

Corridors, a great education resource, are even agreater resource when not bisected by roadways.Teachers can focus on teaching rather than worryingabout students wandering across roadways. Corridorscan be used to connect urban and rural areas. Asour society becomes increasingly urbanized, peoplelose contact with natural ecosystems and theagricultural practices that sustain human life.Corridors that originate in cities and towns and passthrough rural environments allow urban residents toexperience natural and agrarian landscapes. Windingthrough a mosaic of hay fields, pastures, and farmbuildings, greenways can provide exposure toagricultural environments (Figure 4-15). Such exposuremay facilitate better understanding and appreciationof farming and ranching, increasing respect forlandscapes that support these activities. Careful traildesign is necessary to protect the property rights oflandowners.

· Safety

· Ecosystem transects

Many landscapes along the eastern seaboard, in theMidwest, and across the South are a rich mosaic ofwoody patches and open fields defined by corridorsof uncut trees along property lines. On the GreatPlains and westward, shelterbelts and windbreaks givea sense of place to homesteads and rootedness tocommunities. These unnantural blocks and baffles ofvegetation punctuate and partition the prairie. Theyprovide a visual structure and scale against whichvastness can be measured. In the West, mountainsdominate the background but it is the flowing lines ofriparian corridors that give human scale to the foothillsand valley floor. Place names like Wood River Valley,Verde Valley, and Snake River Plains attest to theimpact of riparian corridors on the regionalconsciousness. Occasionally the visual richness ofa riparian corridor is extended into the uplands bycanals, ditches, and grassed waterways.

Corridors also enhance scenic quality at amore intimate scale. Roadsides, railroadROWs, canal banks, and field bordersvegetated with native plants add texturaldiversity and seasonal color that enrich ourexperience of the landscape. Corridors alsoscreen unsightly areas and buffer noise fromhighways and other sources. They make asignificant contribution to the quality of rurallife.

· Spatial structure

· Sense of place, identity

· Complexity, legibility, coherence, andmystery

· Seasonal diversity

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AESTHETIC VALUE ADDED BENEFITS OF

CONNECTIVITY

The added visual amenities provided by a system ofconnected corridors include:

· Enhanced sense of place

· Link to cultural resources

One lesson painting has taught us is that all thingsare connected. A composition is created by lines,forms, colors, and textures that knit the diverse ele-ments of the painting together into a unified composi-tion. As observers of paintings, humans are frequentlyfascinated with the skills the artist used to achieveunity.

Connected corridors, particularly wooded corridors areimportant lines and forms that unify diverse elementsin the landscape. Research by Steven and RachelKaplan suggests that people prefer landscapes thatexhibit coherence, complexity, legibility and mystery.Connected corridors can create these qualities . Alandscape of linked corridors and patches is a legiblelandscape that humans can comprehend andappreciate.

The Minnesota Valley National Wildlife Refuge is adominant visual element for those living in the TwinCities metropolitan region (Figure 4-16). Similarly,the Big Sioux River riparian corridor in eastern SouthDakota is a visual reference for residents in this ruralarea.

Figure 4-16: The broad expense of river, floodplain, bluffs,and prairie make the Minnesota Valley NWR a visual referencefor Twin City residents.

ECONOMIC BENEFITSNatural corridors provide economic benefits and valuesbecause they satisfy human wants or needs. Often,these values are not readily apparent and are difficultto estimate because they are not traded on a market.Researchers Thibodeau and Ostro used cost/benefitanalysis techniques to calculate the value of wetlandsin the Charles River riparian corridor near Boston. Theyestimated the value of land cost increase, watersupply, flood prevention, pollution reduction, andrecreation at between $153,000 and $190,000 per acre.They noted that some of these benefits were realizedby owners of wetlands in the corridor, however, themajority of benefits accrued to the larger communitywithin the watershed.

Linked remnant corridors of woody vegetationin the upper Midwest, east coast, andsoutheast are visual reminders of historiclandscape. Because many of these corridorsare still linked, they have a scale thatprojects an impression far more powerful thandisconnected, isolated remnants.

Research has also shown that peopleappreciate rural settings that have a mixtureof cultural and natural resources. Old roads,stone walls, canals, cemeteries and similarhistoric structures are often concentrated incorridors, and can be incorporated into aconservation corridor program that protectsboth biological diversity as well as historical

character (Figure 4-17). A value-added benefit ofconnectivity is that we can protect the special senseof place that rural areas enjoy by protecting existingconnections and by re-establishing historic linkages.

Figure 4-17: The ruins of this pre-historic Native Americancommunity are located adjacent to the Verde River floodplainin Arizona.

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ENVIRONMENTAL SERVICES

Productive topsoil is arguably this country�s mostvaluable resource. An estimated 240 million tons oftopsoil are eroded annually from Iowa farms andwashed into the Missouri River. In a 1992 report, theNational Research Council suggested grassedwaterways, field borders, buffer strips, conservationterraces, and other introduced corridors that reducesoil erosion and sedimentation can make a significantcontribution to the long-term economy of ruralwatersheds.

Sediments deposited over river bottom sand and gravelbeds are a major cause of decline in Midwest aquaticspecies diversity. Reduced levels of sedimentationimprove fisheries and enhance their economicrevenues. Lower sediment loads also reduce the rateof filling in reservoirs, canals, and drainage ditchesprolonging their utility. The economic returns fromthese various environmental services can besubstantial.

INCREASED YIELDS AND QUALITY

Corridors, like shelterbelts, grassed waterways,terraces, and other corridor type conservation practicesgenerate economic returns exceeding the cost ofinstallation and maintenance. In a study in Kansasand Nebraska, small grain production on the leewardside of windbreaks increased between 18 to 38% fora distance of 3 to 10 times the windbreak height. In a6-year study in Nebraska, researchers estimated a15% yield increase in winter wheat in fields protectedby shelterbelts. They estimated that shelterbeltswould pay for themselves within 15 years.

Increases in yield of 5 to 50% and improved crop qualitywere reported by agronomists for vegetable andspecialty crops protected by windbreaks. Additionally,the climate modification produced by shelterbeltsenhanced production of orchard and vineyard crops.Shelterbelts also produce microclimates that reducestress and increase fitness in livestock and increasehoneybee pollination and honey production.

· Environmental services· Increased crop yields· Increased crop quality· Increased livestock production· Improved livestock health· Reduced energy consumption· Increased property values· Recreation revenues

Shelterbelts provide protection from wind and snowincreasing survival of newborn sheep and cattle. Thesebenefits are maximized when livestock are corralledoutside the windbreak on the lee side.

REDUCED ENERGY CONSUMPTION

Home heating is a major consumer of energy in ruralresidences and small communities (Figure 4-18).Properly located and designed windbreaks are a cost-effective way of lowering home energy consumptionby 10-25%. Windbreaks can also reduce the timeand energy required to remove snow from around farmbuildings and rural roads; saving money and improvingfarm efficiency. Windbreaks on the outskirts of smallrural communities in the northern states protectstructures and significantly reduce snow removal costs.

AGROFORESTRY PRODUCTS

Products obtained from windbreaks, riparian buffers,alley cropping, and woodlots are valued in billions ofdollars, annually. Farmers, applying agroforestryprinciples, plant and manage tree and shrub speciesthat bare edible fruits, nuts, and berries. Theseproducts are harvested and sold in local markets or tolarge commercial outlets. Trees in corridors are alsoharvested for fuel, pulp, posts, speciality woods likewalnut, and for use in the horticultural industry.Mushrooms and medicinal plants like ginseng grownin the shade beneath corridor trees are high pricedcommodities marketed in many regions.

Marketable products can also be obtained from grasscorridors. The seed of some native grass species isa high value commodity. In Iowa, for example, the1998 price of switchgrass seed was $17.00 a pound.Statewide production was unable to meet demand.Wildflowers, native grass stalks, and dried forbs arealso harvested in grass corridors and sold in localmarkets and craft outlets. Providing products for thecraft industry is a growing enterprise.

Figure 4-18: Windbreaks surrounding this rural subdivisionreduce energy consumption during the winter months and lowersnow removal costs.

Benefits from introduced corridors include:

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RECREATION REVENUES

Trails along corridors can also be important generatorsof revenue. A 1988 study of the Elroy-Sparta bicycletrail in Wisconsin found that users spent approximately$15 per person per day for trail related expenses foran overall annual economic impact of $1,257,000. InMinnesota, where trail networks are being expanded,the number of local bed and breakfast accommodationscatering to trail users has exploded. The revenuesthese small businesses generate in rural towns canhave a significant impact on the local economy andprovide employment opportunities for the area�s youngpeople. Economic benefits are increased whencorridors provide a variety of recreational options, fromfloating a river to hiking on a trail. In Montana, visitorsto the upper Missouri Wild and Scenic River and Lewisand Clark National Historic Trail contribute $750,000annually to the economy of the area.

The National Research Council estimated the annualeconomic value of fishing on flowing waters in theUnited States at $8 billion. Hunting also generatessignificant revenues. Researchers estimated anannual value for wooded draws in the Great Plains at$26 million for deer hunting and $1 million for turkeyhunting. Kansas windbreaks generate an annual netvalue of $21.5 million for hunting. Many landownersrealize direct economic benefits by charging rod orgun fees or leasing hunting or fishing rights on theirproperty. Some landowners use a portion of theserevenues to enhance habitat on their farm or ranch.

Bird watchers and other non-consumptive users ofwildlife resources alsocontribute to the localeconomy. Motel rooms inNorth Platte, Nebraska filledwith bird watchers are at apremium during the springsandhill crane migration.Economists estimated activebirders spend between$1,500 and $3,400 on birdingeach year; often theiractivities are in or adjacent tocorridors (Figure 4-20).

INCREASED PROPERTY VALUES

Land appraisal information and research findingssuggest property adjacent to amenities like ripariancorridors is valued higher than property withoutproximity to these amenities (Figure 4-19). In westernstates, river and stream frontage property is in highdemand, short supply, and 25 to 50% more expensivethan property without frontage. Economists Fausoldand Lilieholm cited numerous examples of significantincreases in property values for land abutting parks orstream corridors. A study of riparian greenbelts inBoulder, Colorado determined that the average valueof property adjacent to the greenbelt would be 32%higher than those 3,200 feet away, all other variablesbeing equal.

The influence of corridors on property values alsoapplies to privately held greenbelt land without publicaccess according to a study done near Salem,Oregon. The greenbelt land in the study wascomposed of rural farmland without trails. The studyconcluded that land adjacent to the greenbelt wasworth approximately $1,200 more per acre than landlocated 1,000 feet away. The increased economicvalue these greenbelts generated was based onenhanced visual quality they provided.

In many cases, restoration or enhancement ofcorridors will be necessary to provide the economicbenefits described. In California, homes situated nearseven stream restoration projects had property values3 to 13% higher than similar homes located onunrestored streams.

Figure 4-20: This series ofpictures depict some of themany recreational opportunitiescorridors can provide.

Figure 4-19: The increased value of homes in this Utahsubdivision can be attributed to their proximity to this openspace corridor.

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POTENTIAL ADVERSE IMPACTSThe list of benefits associated with corridors isimpressive and well documented. There are however,potential adverse impacts that may originate incorridors:

· Crop damage· Disease and weed infestations· Predation/parasitism· Social impacts· Visual impacts

Many of these impacts can be mitigated through properplanning, design, and management.

CROP DAMAGE

There is a perception in rural America that untendedvegetation in natural patches and corridors is a majorsource of insects that infest crops. Corridors do infact provide habitat for both pest and beneficial speciesof insects. Occasionally pest populations in corridorserupt causing significant damage to adjacent crops.Researchers in Texas reported a $50 per acrereduction in cotton yields in fields adjacent towindbreaks that overwintered large populations of bollweevils (Anthonmus gradis). Alfalfa weevils (Hyperapostica) which also overwinter in windbreak litter cancause similar reductions in alfalfa production.

Birds and mammals that inhabit or move throughcorridors can also damage crops in the adjacentmatrix. Some evidence suggests that crop lossescaused by birds is higher in fields adjacent towindbreaks. Damage to grain and forage crops bydeer and elk is a significant problem in many states.In Wisconsin, most farmers report only a few hundreddollars worth of deer damage to corn and hay cropseach year. However, in areas where deer densitiesapproach 90 deer per square mile, damage claimsaverage $9,000 per farm. Browsing deer, elk, rabbits,and rodents can also injure or kill nursery and orchardstock. Beaver frequently raise havoc with trees inurban greenways and decimate expensive stream

restoration projects (Figure 4-21). However, in othersettings, beaver can beimportant in watershedrestoration and provide animportant succession ofsnags for wildlife.

DISEASE AND WEED CONDUIT

Simberloff (in Mann and Plummer) noted that corridorscan be conduits for diseases, predators, exoticspecies, and fire. Poorly managed roadside corridorsare notorious conduits for noxious weeds (Figure 4-22). Seeds and suckers from corridors may spreadinto the adjacent matrix. For example, cheatgrass(Bromus tectorum) dominates many roadsides in theGreat Basin and spreads rapidly into abuttingrangeland. This early curing, flashy fuel is the ignitionsource for many range fires.

PREDATION / PARASITISM

Narrow corridors are prone to high levels of predationand parasitism. Biologist Best reported that 29% ofthe songbird nests in an Iowa study plots wereparasitized by brown-headed cowbirds (Molothrusater). Large ground nesting birds like the ring-neckpheasant and ducks may be particularly susceptibleto predation in corridors. In one eastern Coloradostudy, an estimated 55% of roadside pheasant nestswere terminated by predation. Biologists acknowledgehigh rates of pheasant mortality in roadsides but arguethat roadsides and other types of strip cover are notsinks; production exceeds losses to predation.

Figure 4-21: This cottonwoodplanting was cut by beaver.

Figure 4-22: The ubiquitous tumbleweed is using this roadsidecorridor to spread into the adjacent desert grassland matrix.

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Michael Soule suggests disease, predation, andparasitism concerns are most applicable forthreatened and endangered species. In highlydeveloped landscapes, he argues the benefits ofcorridors for most species far outweigh theirpotential adverse impacts.

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SOCIAL IMPACTS

Riparian corridors seem to be particularly susceptibleto adverse impacts from recreation (Figure 4-23). Thehigh levels of recreation activity in some ripariancorridors may be sufficient to displace some speciesof wildlife. Often the vacated habitat niches areoccupied by less desirable species. Intense recreationactivity may also lead to the degradation of thecorridor�s ecosystem with potentially long-termadverse consequences.

VISUAL IMPACTS

The alignment and management of some corridorsproduce highly contrasting lines and forms in thelandscape. Highway, pipeline and powerline corridorsrouted through forests frequently produce unsightlyswaths. Power transmission lines that march acrossfarmland and prairie are viewed as equally unattractive.In some cases, woody introduced corridors blockdesirable views.

OTHER POTENTIAL IMPACTS

Networks of corridors may not always bedesirable. For example, two spatially separatedpopulations of the same species may each havedeveloped different genetic adaptations to theirunique environmental condition. If these patchesare linked and species move between them andinterbreed, these adaptations could be lost. Bothpopulations could decline or go extinct.

These potential adverse impacts may be inherentin corridors or the way society chooses tomanage them. Many can be mitigated byconsulting with biologists when planning,designing, and managing corridors.

CORRIDOR BENEFITSSUMMARYCorridors within a watershed provide a multitude ofeconomically and socially significant benefits forindividual landowners and the larger community.Many of these benefits are complementary but, notinfrequently, they conflict; intense recreation andwildlife habitat, for example. Reed Nossacknowledges these potential conflicts and arguesthat the primary goal for conservation corridors ingeneral should be to preserve and enhancebiological diversity. Corridors are not a panacea; alandscape of corridors is a landscape populatedby edge species and limited in its diversity.Patches of plant community types indigenous to a

watershed and large enough to support viablepopulations of native wildlife species within a wellmanaged matrix are essential to maintainingbiodiversity.

The challenge for land managers is to accommodateuses compatible with corridor resources whilemaintaining the ecological integrity of existingcorridors. Planting new corridors to conserve soil andwater and to provide connectivity between patches forvulnerable species of wildlife will be equally important.The challenge must be extended to conservationof existing patches, patch restoration andecologically sound management of the matrix.This will require a detailed knowledge of corridor andpatch resources, management practices, userdemands, and landowner and agency concerns. Thefollowing chapters in this handbook outline a planningprocess that will address these issues at bothwatershed and conservation plan scales. Asrecommended by the National Research Council in1992, the process emphasizes the integration ofexisting conservation practices to optimize the benefitscorridors provide (Figure 4-24).

Figure 4-24: Boulder Creek, Boulder Colorado is a model of integratedriparian corridor resource planning

Figure 4-24:

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Figure 4-23: This riparian corridor has been severely impactedby fishermen and other recreationists.

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MANAGE THE MATRIX WITH

WILDLIFE IN MIND.

NATURAL CONNECTIVITY SHOULD BE

MAINTAINED OR RESTORED.

NATIVE SPECIES ARE BETTER THAN

INTRODUCED SPECIES.

Case Study:

PEQUEA - MILL CREEK WATERSHED

Corridor Planning Principles discussed in Chapter 5 that are exhibited by this casestudy include:

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Case Study: Pequea - Mill Creek Watershed

This case study illustrates how an extensivewatershed wide partnership coordinated by NRCShas produced and implemented a plan forrestoring 37 miles of stream corridor and adjacentuplands. The conservation project, an on-goingeffort, continues to provide economic, wildlifehabitat, recreation, and aesthetic benefits towatershed residents.

The Pequea�Mill Creek watersheds are locatedin central Lancaster County in south�centralPennsylvania. The case study project areaencompasses approximately 135,000 acres.Dairy farming is the dominant agriculturalenterprise with 55,000 dairy cows distributedamong 1,000 small farms located in thewatershed.

The Pequea�Mill Creek Hydrological Unit AreaProject, initiated in 1991, is focused on reducingpotential nutrient, sediment, and bacterial lossesfrom concentrated livestock areas aroundfarmsteads and nutrient and pesticide managementin crop fields. Barnyard management, streambankfencing, armored stream crossings, restoration ofriparian plant communities, and grazing areamanagement have been emphasized to reducecontamination from farmsteads.

These watersheds were selected under USDA�sWater Quality Initiative to coordinate and increasea voluntary approach reducing agricultural nonpointsource pollution. Partners in this effort includeCooperative Extension, NRCS, Farm ServiceAdministration, Lancaster County ConservationDistrict, Pennsylvania Game Commission,Pennsylvania Department of Environmental Qualityand numerous other agencies working with farmers,township officials and homeowners.

A partial list of accomplishments to date includes:

· Improved water quality

· 538 farmers have installed at least oneconservation practice

· 180 farmers have developed contracts toinstall conservation practices

· 37 miles of stream have been fenced toexclude livestock on 84 farms incooperation with the Pennsylvania GameCommission, U.S. Fish and WildlifeService, and Lancaster CountyConservation District

· 25 rotational lot management systemshave been implemented to reduce theamount of runoff from livestock exerciseareas

· Demonstrations of stream crossings,livestock watering and shading optionshave been developed with the LancasterCounty Conservation District

· Information and education programs havebeen focused on farmer participation withinvolvement from the private sector in waterquality efforts

Figure 2: The same reach of creek after exclosurefencing and revegetation.

Figure 1: The impacts of large numbers of cattle concentrated ina riparian zone for long periods of time can be devastating.

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Lancaster County, Pennsylvania

There are many other benefits from streambankfencing and planting in riparian corridors in additionto improved water quality. In the Pequea�Mill CreekProject, many farmers have learned that streambankfencing is an integral part of an effective dairymanagement program. For example, one significantbenefit of streambank fencing has been improveddairy herd health. As one local expert says: �Thereis nothing in the stream that is good for cows andthere is nothing the cows do that is good for thestream.� The Pennsylvania Game Commission hasstocked trout in restored sections of the creekproviding future recreation benefits for arearesidents.

Participants in the project report that streambankfencing and other conservation practices have:

· Improved dairy herd health

· Stabilized streambanks and reduced soilerosion

· Provided wildlife habitat

· Improved water quality

· Improved fish habitat

· Promoted rotational grazing

Water is a shared resource. Byimproving a stream, downstreamneighbors benefit. Fencing sets agood example, encouraging upstreamneighbors to protect their streams.Well-kept streams also make a goodimpression and provide a positiveimage of farms to the public.

For more information contact:

Pequea�Mill Creek Project307 B Airport DriveSmoketown, PA 17576-0211Tel. (717) 396 � 9423Fax. (717) 396 � 9427

The information for this case study was abstracted withpermission from Pequea�Mill Creek Information Series Bulletins28 and 30 prepared by Pennsylvania State University, Collegeof Agricultural Science, Cooperative Extension Service incooperation with USDA Natural Resources ConservationService.

Figure 3: Trout, songbirds, and butterfliesinhabit this restored reach of Mill Creek.F

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Case Study:

JEFFERSON COUNTY OPEN SPACE PLAN

CONNECTED RESERVES / PATCHES

ARE BETTER THAN SEPARATED

RESERVES / PATCHES.

LARGE RESERVES / PATCHES ARE

BETTER THAN SMALL

RESERVES / PATCHES.

SEVERAL RESERVES / PATCHES

(REDUNDANCY) ARE BETTER THAN

ONE RESERVE / PATCH.

INTRODUCED CONNECTIVITY SHOULD

BE STUDIED CAREFULLY.

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Edge

Corridor Planning Principles discussed in Chapter 5 that are exhibited by this casestudy include:

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Case Study: Jefferson County Open Space Plan

This case study illustrates the value of regionalscale open space planning in rapidly urbanizingwatersheds. Conservation, enhancement, andrestoration of wildlife habitat is an integral part ofthe Jefferson County Open Space Plan.Conservation corridors are a key element in linkingdispersed patches of wildlife habitat. NRCS playsa major role in providing technical assistance asthe plan continues to evolve.

Jefferson County, a progressive and rapidlyurbanizing county near Denver, Colorado, initiatedan open space preservation program during the early1970s (Figure 1). This program is funded by a one-half percent sales tax on retail sales in JeffersonCounty. The goal of the Jefferson County OpenSpace Program is to preserve open space as aliving resource for present and future generations.The primary objectives of the program are to acquireand maintain lands, to ensure the quality of life inthe county by providing open space for physical,psychological, and social enjoyment, and preservingthe natural and unique landforms that defineJefferson County.

The Jefferson County Open Space planning processis inclusive and collaborative involving many differentstakeholder groups. Specific goals and objectiveswere established through interviews with a varietyof groups and extensive public scoping meetings,which provided guidance for the inventory process.Using a geographic information system, inventorymaps were prepared and include:

· Existing and proposed open space,parks, and trails

· Key land uses and activities

· Wildlife, archeological, historic, andcultural features

· Vegetation, surface water, and floodplains

· Landforms and geologic hazards

· Existing and proposed roads andinfrastructure

· Slopes and viewsheds

From the inception of the Open Space Program,the NRCS has played a valuable role in providinginventory data, data evaluation, and technicalassistance. Specific NRCS assistance included:

· Soils information

· Vegetative inventories

· Revegetation plans (native, pasture,hayland, post-wildfire)

· Erosion control (gully, streambank,disturbed upland areas)

· Pasture/hayland management

· Grazing management for nativegrasslands

· Plant materials

· Pond/water development

· Wildlife habitat development/improvement

The planning process identified lands that shouldbe preserved or managed to provide habitat forvalued wildlife species (Figure 2). The proximityof critical habitat lands to urban development,roads, and other recreational resources helpeddetermine the appropriate level and type ofmanagement necessary to protect wildlifepopulations. Mapping wildlife habitat provided avaluable point of discussion between the OpenSpace Department and appropriate wildlifeagencies regarding management and acquisitionoptions.

Figure 1: A view of urban development from one of theJefferson County Open Space Parks.

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Golden, Colorado

The plan identified five types of open space andtrails. Regional preserves are the keystoneelements for the protection of wildlife. They aregenerally large (> 500 acres) and intended to protectthe natural resource or unique feature. Regionalpreserves are reserved primarily as open space/habitat with development limited to less than 20%of the site. They protect floodplains, breedingareas, relict plant communities, rare andendangered species habitat, and other sensitiveresources. Corridors, some with trails, are beingdeveloped to connect these significant resourceareas enhancing their value for both wildlife andrecreation.

Over the 25 years of its existence, the JeffersonCounty Open Space Program has acquiredapproximately 32,000 acres and has constructedover 100 miles of trails (Figure 3). This programdemonstrates successful protection of wildlifehabitat can be combined successfully with otheruses such as recreation and aesthetics in urban/suburban landscapes. The program also illustratesthe importance of building diverse partnerships toaccomplish program goals in an urban context.

For more information contact:

Jefferson County Open Space18301 West 10th AvenueSuite 100Golden, CO 80401

The information for this case study was abstracted withpermission from Jefferson County Open Space brochuresprepared by the Department of Jefferson County Open Spaceand from The Jefferson County Open Space Master Plan,1989, prepared by BRW, 4643 South Ulster St., Suite 1180,Denver, CO and Urban Edges, 1624 Humboldt St., Denver,CO.

Figure 2: Mapped critical habitat and wetlands withinJefferson County.

Figure 3: A map of existing protected habitat areas andproposed acquisition areas.

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