4 OUTDOOR CALIFORNIA May - June 2003

By Matthew D.Johnson

The chance to restore asalt marsh is exciting,but when it comes at

the cost of losing seasonally-flooded grassland heavilyused by raptors, the prospect

northwestern California hasbeen converted to pasture,hay production, and citydevelopments. Now, DFG andthe City of Arcata have anopportunity to restore about250 acres along the northernedge of the bay in an areaknown as McDaniel Slough.Together, they have proposeda salt marsh restorationproject that involvesbreaching levees along thebay and allowing high tidesto inundate McDaniel Sloughwith salt water. Tidal actionwill then naturallyreintroduce salt marsh plantsto the area and restore saltmarsh habitat for shorebirds,fish, benthic organisms, andrare salt marsh plants such asthe Humboldt Bay owl’s-clover (Castilleja ambigua ssp.humboldtiensis).

The plan has not beenuniversally praised, however,because an impressive,seasonally flooded perennial

grassland has developed onthe property since it wasacquired in 1988 by DFG forwetland management. Studiesconducted by HSU studentshave documented abundantrodent populations,including the highestdensities of California voles(Microtus californicus) everreported. Consequently, thearea is an important huntingground for several raptorspecies, especially theNorthern Harrier (Circuscyaneus), the White-tailedKite (Elanus leucurus), andthe Short-eared Owl (Asioflammeus), and it is a populardestination for local birdwatchers.

To help provide hard datato what at times has been aheated debate — raptorsversus salt marsh — 25students from HSU’s WildlifeHabitat Ecology class andtheir instructor undertookan ambitious project to

predict how wildlife mightrespond to the twomanagement scenariosproposed for the area. Thefirst scenario involved anarrow breach in the levee,creating a “muted” tidal flowinto the salt marsh; thesecond included a widerbreach and less restricted“full” flow. The students firstused aerial photography,elevation maps, andtopography survey dataprovided by city officials topredict how vegetation mayrespond to the different leveebreaching proposals. Then,using a sophisticatedcomputer software programadministered by DFG calledthe California WildlifeHabitat Relationships System(CWHR), the students wereable to compare and contrasthow individual wildlifespecies respond to eachscenario. The CWHR containsenough detail for users to

becomes more complicated,or so the CaliforniaDepartment of Fish andGame (DFG) and Arcata cityofficials have learned. A groupof wildlife and city managers,with the help of a classproject conducted byundergraduate wildlifestudents from HumboldtState University (HSU), areforging a plan to balancehabitat for both salt marshand grassland plants andanimals.

Over the past 130 years, 87percent of the salt marsharound Humboldt Bay in

Photo © Matthew D. JohnsonPhoto © Andrea Pickart

OUTDOOR CALIFORNIA 5May - June 2003

evaluate the relative benefitsof various managementscenarios, but it does notmake value judgments abouthabitat suitability forwildlife in general. Finally,the students proposed a thirdscenario that could reach acompromise preservinghabitat for raptors whileproviding salt marshrestoration.

The students’ findingssuggested that the muted-flow scenario would providebetter wildlife habitat for themajority of the over 200species listed as dependent onthe area than a full-flow oftide water into the marsh.Under the full-flow scenariovery little of the 250 acreswould support plant lifebecause much of the landinside the levees is too low inelevation. Instead, the full-flow option would create over180 acres of tidal mudflat, arelatively abundant habitat

around the bay. In contrast,the muted-flow scenariowould result in the creationof about 90 acres of saltmarsh, of which about 15acres would be favorable forrare plants based onelevational distribution data.However, even this scenariowould destroy grasslands andcreate over 120 acres ofmudflats, so the studentsexplored a third option.

Proposing a change in thearrangement of one levee toretain a strip of existinghabitat on the western side ofproject, the students used theCWHR computer program topredict how wildlife mightrespond to their so-calledGreen and Gold scenario,

named for HSU’s schoolcolors. This scenario wouldpreserve almost 100 acres ofgrassland and still allow thecreation of about 70 acres ofsalt marsh, nearly the sameamount as under the muted-flow scenario proposed byArcata and DFG. All of theroughly 15 acres suitable forrare plants would also beretained. Their results suggestthat while wildlife wouldrespond well to all threescenarios due to the creationof new wetlands habitats, thegreatest benefit would comefrom the Green and Goldscenario, with over twice asmany species positively asnegatively affected. Inparticular, the students’

scenario painted acomparatively bright futurefor animals reliant ongrassland habitats (e.g.,raptors and small mammals),which would likely bedisplaced by the other twoscenarios. (Full details areavailable in a 50-page report,McDaniel Slough project,available on-line atwww.humboldt.edu/~mdj6/WLDF431.html).

The City of Arcata andDFG are currently preparingenvironmental impactstatements for the proposal.The exact arrangement oflevees is still somewhatflexible, but they will likelyfollow the muted flowscenario fairly closely.

Photo © Klaus J. Beyer

Above, terns.

Far left, Owl’s-clover. Middle, grasses in thearea. Right, slough in Humboldt Bay Area.

Photo © Andrea Pickart

6 OUTDOOR CALIFORNIA May - June 2003

Nonetheless, the students’scenario has the addedbenefit of potentially savingmoney by requiring lesslinear feet of new leveeconstruction, and elementsof their design may beincorporated into the finaldesign. Construction isexpected to begin in 2004.

Although all threescenarios would likelyincrease local wildlifediversity, some local citizenscorrectly noted that westernsalt marshes support fewerwildlife species, and moreanimals could be attracted tothe area by creating freshwater marsh. Moreover,newly created salt marshhabitat will probably becolonized by non-nativecordgrass (Spartinadensiflora), a South Americangrass used little by nativeCalifornia wildlife. However,the students’ report filed toDFG suggested that if theupper reaches of the marshcould be kept free of theinvasive grass, endemic andrare salt marsh plants mightbe supported. And theseplants, such as Point ReyesBird’s Beak (Cordylanthusmaritimus ssp. palustris),make more substantivecontributions to statewidebiodiversity than dovirtually any of the wildlifespecies because the animals

are very widely distributedand comparatively common.Moreover, grasslands can andare being preserved elsewherearound the bay, whereasopportunities for salt marshrestoration arise in only afew places, such as atMcDaniel Slough.

The students’ results areintriguing, but theycautioned that many of theirfindings rely on a fewassumptions, especially onerelated to the tidal elevationsabove which salt marshplants can take root. Theyrecommended thatadditional surveys byqualified hydrologists beconducted to betterunderstand the elevation atwhich salt marsh plants cansecure a foothold on tidalmudflats.

The project demonstratesthat when universities, cities,and DFG work cooperatively,everyone can benefit. UsingDFG’s CWHR computermodel, the students learnedvaluable skills useful forfuture employment, andtheir report will be helpful tothe managing agencies asthey plan and complete theproject.

Matthew D. Johnson is an assistantprofessor for the Department ofWildlife at Humboldt State.University.

Townsend’s Big-Eared BatVagrant ShrewGolden-Crowned SparrowWhite-Crowned SparrowLoggerhead ShrikeMerlinWrentitViolet-Green SwallowRed-Throated LoonRed-Necked GrebeNorthern MockingbirdBand-Tailed PigeonHorned GrebeBrandt’s CormorantAmerican KestrelTundra SwanFringed MyotisLittle Brown MyotisHairy WoodpeckerChestnut-Backed ChickadeeTownsend’s WarblerWestern TanagerBullock’s OrioleCommon PorcupineNorthern Saw-Whet OwlRed-Breasted SapsuckerAmerican RobinCedar WaxwingBlack-Throated Gray WarblerWhite-Faced IbisStilt SandpiperRufous HummingbirdCommon NighthawkEnsatinaPacific-Slope FlycatcherAsh-Throated FlycatcherWinter WrenCassin’s VireoMacgillivray’s WarblerYellow-Breasted ChatDark-Eyed JuncoLong-Legged Myotis

Hoary BatDusky-Footed WoodratFoothill Yellow-Legged FrogRuby-Crowned KingletHermit ThrushVaried ThrushNorthern Pygmy OwlRaccoonRing-Necked DuckTree SwallowWestern Wood-PeweeHouse FinchSpotted TowheePacific Giant SalamanderWhite-Tailed KiteShort-Eared OwlAnna’s HummingbirdAllen’s HummingbirdWillow FlycatcherHutton’s VireoBushtitMourning DoveCalifornia Slender SalamanderElegant TernDowny WoodpeckerBewick’s WrenSwainson’s ThrushWarbling VireoYellow WarblerBlack-Headed GrosbeakVirginia OpossumGreat Horned OwlWilson’s WarblerMallardBobcatLazuli BuntingHouse WrenOrange-Crowned WarblerWood DuckEuropean StarlingRed KnotWestern Fence Lizard

List of species predicted to be positively affected byMcDaniel slough change from current condition to “Green &Gold” scenario based on CWHR analysis (in order ofincreasing positive effect):

Photo © Jack H. TasoffVirginia rail. Cedar waxwings.

OUTDOOR CALIFORNIA 7May - June 2003

American BitternLong-Eared MyotisGreater White-Fronted GooseEurasian WigeonCinnamon TealCommon MerganserSpotted SandpiperAmerican PipitRuddy DuckHooded MerganserNorthern Rough-Winged SwallowWestern Terrestrial Garter SnakeThayer’s GullBlack PhoebeGreen HeronOldsquawHeermann’s GullCommon YellowthroatNorthwestern SalamanderWestern Pond TurtlePacific Coast Aquatic Garter SnakeNorthern HarrierRough-Skinned NewtCommon LoonBarn SwallowLong-Billed CurlewGlaucous-Winged GullMew GullSurf ScoterRed-Breasted MerganserWestern GullCaspian TernDouble-Crested CormorantCommon SnipeSemipalmated PloverRuddy TurnstoneBlack TurnstoneBaird’s SandpiperPectoral SandpiperRed-Necked PhalaropeRed PhalaropeRedheadGreat Blue HeronBelted KingfisherGreater ScaupWhite-Winged Scoter

Herring GullHarbor SealWestern GrebeClark’s GrebeBonaparte’s GullCliff SwallowBald EagleVirginia RailBuffleheadCommon TernOspreyPied-Billed GrebeCanvasbackBlack-Bellied PloverWhimbrelSoraCommon GoldeneyeMarsh WrenKilldeerNorthern PintailGreat EgretBrantWilson’s PhalaropeBlack-Necked StiltPacific Golden-PloverLong-Billed DowitcherDunlinSong SparrowWestern SandpiperGreater YellowlegsLesser YellowlegsAmerican AvocetNorthern River OtterRing-Billed GullShort-Billed DowitcherLeast SandpiperForster’s TernWilletMarbled GodwitEared GrebeAmerican CootCalifornia GullBlack-Crowned Night HeronSnowy EgretAmerican Mink

Photo © Brian Murphy

Photo © Dave PattonAnna’s hummingbird.

Photo © Siegfried MatullRacoon.