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Restor­ing preda­tors and prey simul­ta­ne­ously accel­er­ates the recov­ery of both

pub­lished 11 March 2017 | mod­i­fied 11 March 2017

Juvenile Steller sea lionsReduc­ing human pres­sure on exploited preda­tors and prey at the same time is the best way to help their pop­u­la­tions recover, a new study indicates.

The find­ings about syn­chro­nous recov­ery are impor­tant because his­tor­i­cally about half the attempts at species restora­tion have amounted to a sequen­tial, one-​species-​at-​a-​time tac­tic — usu­ally the prey species first, then the predator.

… syn­chro­nous recov­ery is ulti­mately bet­ter for recov­er­ing the ecosys­tem, and bet­ter from an eco­nomic per­spec­tive as well
Mark Novak, co-​author, Depart­ment of Inte­gra­tive Biol­ogy, Ore­gon State Uni­ver­sity, Ore­gon, USA »

This study sug­gests that a syn­chro­nous approach almost always pro­duces a recov­ery that is more rapid and more direct — faster than predator-​first recov­ery and less prone to volatile pop­u­la­tion fluc­tu­a­tions than prey-​first recov­ery. Just as cru­cial, syn­chro­nous is also bet­ter for the humans who earn a liv­ing har­vest­ing the two species. The find­ings of the research are pub­lished online on 1 March in the jour­nal Nature Ecol­ogy and Evo­lu­tion.

You might think the loss of income asso­ci­ated with reduc­ing har­vest on both species at the same time would be greater than reduc­ing har­vest on one species after another, but our work sug­gests that syn­chro­nous recov­ery is ulti­mately bet­ter for recov­er­ing the ecosys­tem, and bet­ter from an eco­nomic per­spec­tive as well,” said Mark Novak of the Ore­gon State Uni­ver­sity Col­lege of Science.

Because of over­har­vest, declines of mul­ti­ple ani­mal pop­u­la­tions — includ­ing at least one species that con­sumes other har­vested species — char­ac­ter­ize many ecosys­tems, Novak notes. Exam­ples of paired pop­u­la­tion col­lapses wholly or par­tially attrib­ut­able to tro­phy hunt­ing, indus­trial fish­eries or the fur trade are lions and wilde­beest; Steller sea lions and Pacific her­ring; and mink and muskrat.

Novak, assis­tant pro­fes­sor of inte­gra­tive biol­ogy, notes that in both ter­res­trial and marine resources man­age­ment, pop­u­la­tion restora­tion and the set­ting of har­vest quo­tas has long been a single-​species endeavour.

Predator prey recoveryCom­mu­nity return time and volatil­ity for three recov­ery sce­nar­ios.
a, Schematic illus­trat­ing the two recov­ery met­rics, com­mu­nity return time and com­mu­nity volatil­ity, used to analyse the effec­tive­ness of alter­na­tive recov­ery strate­gies. b,c, Com­mu­nity return times (years) (b) and com­mu­nity volatil­i­ties (dimen­sion­less) (c) for the base­line case under three recov­ery sce­nar­ios. See Meth­ods of orig­i­nal arti­cle for para­me­ter val­ues and def­i­n­i­tions of recov­ery met­rics. Note that these pat­terns are gen­er­ally robust even if the lag time between recov­ery of the preda­tor (prey) and ces­sa­tion of exploita­tion of the other species is elim­i­nated (see Sup­ple­men­tary Infor­ma­tion of orig­i­nal arti­cle).
Source: Jameal F. Samhouri et al., 2017. Rapid and direct recov­er­ies of preda­tors and prey through syn­chro­nized ecosys­tem man­age­ment.

Even in the more holis­tic ecosystem-​based rebuild­ing of food webs — the inter­con­nected chains of who eats whom — the dom­i­nant strat­egy has been to release pres­sure at the bot­tom, let­ting prey pop­u­la­tions return to the point where they ought to sus­tain the top preda­tors more read­ily, Novak said.

Col­lab­o­ra­tors at the National Marine Fish­eries Cen­ter, includ­ing Shan­non Hen­nessey, now a grad­u­ate stu­dent at OSU, led the study, which points out the lim­i­ta­tions of both of these philoso­phies. It also high­lights the room for improve­ment in pol­icy tools that syn­chro­nous recov­ery man­age­ment could fill.

(Source: Ore­gon State Uni­ver­sity news release, 27.02.2017)

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