AboutZoos, Since 2008


Inva­sive species: Not always the enemy

pub­lished 31 May 2014 | mod­i­fied 31 May 2014

Efforts to erad­i­cate inva­sive species increas­ingly occur side by side with pro­grams focused on recov­ery of endan­gered ones. But what should resource man­agers do when the erad­i­ca­tion of an inva­sive species threat­ens an endan­gered species?

California clapper railIn a new study pub­lished May 30 in the jour­nal Sci­ence, researchers at the Uni­ver­sity of Cal­i­for­nia (UC), Davis, exam­ine that conun­drum now tak­ing place in the San Fran­cisco Bay. The Cal­i­for­nia clap­per rail – a bird found only in the bay – has come to depend on an inva­sive salt marsh cord­grass, hybrid Spartina, for nest­ing habi­tat. Its native habi­tat has slowly van­ished over the decades, largely due to urban devel­op­ment and inva­sion by Spartina.

Their results showed that, rather than mov­ing as fast as pos­si­ble with erad­i­ca­tion and restora­tion, the best approach is to slow down the erad­i­ca­tion of the inva­sive species until restora­tion or nat­ural recov­ery of the sys­tem pro­vides appro­pri­ate habi­tat for the endan­gered species.

Just think­ing from a single-​species stand­point doesn’t work
Alan Hast­ings, co-​author, pro­fes­sor envi­ron­men­tal sci­ence and pol­icy at UC Davis »

“The whole man­age­ment sys­tem needs to take longer, and you need to have much more flex­i­bil­ity in the tim­ing of bud­getary expen­di­tures over a longer time frame,” said Hastings.

The sci­en­tists com­bined bio­log­i­cal and eco­nomic data for Spartina and the clap­per rail to develop a mod­el­ling frame­work to bal­ance con­flict­ing man­age­ment goals, includ­ing endan­gered species recov­ery and inva­sive species removal, given bud­getary constraints.

While more threat­ened and endan­gered species are becom­ing depen­dent on inva­sive species for habi­tat and food, exam­ples of the study’s spe­cific con­flict are rare. The only other known case where the erad­i­ca­tion of an inva­sive species threat­ened to com­pro­mise the recov­ery of an endan­gered one is in the south­west­ern United States, where a pro­gram to erad­i­cate tamarisk was can­celled in areas where the inva­sive tree pro­vides nest­ing habi­tat for the endan­gered south­west­ern wil­low fly-​catcher. “As erad­i­ca­tion pro­grams increase in num­ber, we expect this will be a more com­mon con­flict in the future,” said co-​author and UC Davis pro­fes­sor Ted Grosholz.

A del­i­cate bal­ance, when remov­ing inva­sive species threat­ens endan­gered species:

(Source: UCDavis YouTube channel)

The sci­en­tists used data from Grosholz’s lab as well as from the Inva­sive Spartina Project of the Cal­i­for­nia Coastal Con­ser­vancy in their analy­sis. Spartina alterni­flora was intro­duced to the San Fran­cisco Bay in the mid-​1970s by the Army Corps of Engi­neers as a method to reclaim marsh­land. It hybridised with native Spartina and invaded roughly 800 acres. Erad­i­ca­tion of hybrid Spartina began in 2005, and about 92 per­cent of it has been removed from the bay. The cord­grass has also invaded areas of Willapa Bay in Wash­ing­ton state, where efforts to erad­i­cate it are nearly com­plete, and inva­sive Spartina has been spot­ted and removed from Toma­les Bay, Point Reyes and Boli­nas Lagoon in California.

The study, led by UC Davis post­doc­toral fel­low Adam Lam­pert, was funded by the National Sci­ence Foun­da­tion Dynam­ics of Cou­pled Nat­ural and Human Sys­tems Pro­gram. “This work is sig­nif­i­cant in advanc­ing a gen­eral, ana­lyt­i­cal frame­work for cost-​effective man­age­ment solu­tions to the com­mon con­flict between remov­ing inva­sive species and con­serv­ing bio­di­ver­sity,” said Alan Tessier, pro­gram direc­tor in the National Sci­ence Foun­da­tion Divi­sion of Envi­ron­men­tal Biology.

(Source: UC Davis news release, 29.05.2014)

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