8 research outputs found
Hemispheric asymmetry in ocean change and the productivity of ecosystem sentinels
Climate change and other human activities are causing profound effects on marine ecosystem productivity. We show that the breeding success of seabirds is tracking hemispheric differences in ocean warming and human impacts, with the strongest effects on fish-eating, surface-foraging species in the north. Hemispheric asymmetry suggests the need for ocean management at hemispheric scales. For the north, tactical, climate-based recovery plans for forage fish resources are needed to recover seabird breeding productivity. In the south, lower-magnitude change in seabird productivity presents opportunities for strategic management approaches such as large marine protected areas to sustain food webs and maintain predator productivity. Global monitoring of seabird productivity enables the detection of ecosystem change in remote regions and contributes to our understanding of marine climate impacts on ecosystems
Hemispheric asymmetry in ocean change and the productivity of ecosystem sentinels
Climate change and other human activities are causing profound effects on marine ecosystem productivity. We show that the breeding success of seabirds is tracking hemispheric differences in ocean warming and human impacts, with the strongest effects on fish-eating, surface-foraging species in the north. Hemispheric asymmetry suggests the need for ocean management at hemispheric scales. For the north, tactical, climate-based recovery plans for forage fish resources are needed to recover seabird breeding productivity. In the south, lower-magnitude change in seabird productivity presents opportunities for strategic management approaches such as large marine protected areas to sustain food webs and maintain predator productivity. Global monitoring of seabird productivity enables the detection of ecosystem change in remote regions and contributes to our understanding of marine climate impacts on ecosystems
Block preconditioners for fully implicit Runge-Kutta schemes applied to the Bidomain equations
Recently, the authors presented different block preconditioners for implicit Runge-Kutta discretization of the heat equation. The preconditioners were block Jacobi and block Gauss-Seidel preconditoners where the blocks reused existing preconditioners for the implicit Euler discretization of the same equation. In this paper we will introduce similar block preconditioners for the implicit Runge-Kutta discretization of the Bidomain equation. We will, by numerical experiments, show the properties of the preconditoners, and that higher-order Runge-Kutta discretization of the Bidomain equation may be superior to lower-order in some cases
Levedyktighetsanalyser for norske lomvibestander
Hekkebestandene av lomvi (Uria aalge) langs norskekysten har hatt en sterk nedgang i lĂžpet
av de siste 45 Ă„rene. Den norske fastlandsbestanden utgjĂžr i dag ikke mer enn ca 15 000 par,
mens den til sammenligning ble beregnet til 120-160 000 par i begynnelsen av 1960-Ă„rene.
Den stÞrste bestanden i norske omrÄder finnes i dag pÄ BjÞrnÞya hvor det hekker ca 100 000
par, men ogsĂ„ her er bestanden betydelig mindre enn i midten av 1980-Ă„rene. Ă
rsaken til
denne bestandsnedgangen er kompleks, og skyldes mest sannsynlig en kombinasjon av klima
og effekter pÄ viktige byttedyr, overfiske av enkelte viktige fiskebestander som lodde og sild,
samt drukning i fiskegarn. En kan heller ikke utelukke at lomvi har vĂŠrt utsatt for oljeskader i
vinteromrÄdene selv om det ikke er klare bevis for det
MĂ„lsetningen med denne undersĂžkelsen har ikke vĂŠrt Ă„ forklare Ă„rsaker til tilbakegangen,
men Ă„ gi kvantitative prognoser for den videre utviklingen til norske lomvikolonier, gitt at
miljÞforholdene og andre pÄvirkningsfaktorer blir de samme i framtida som de var i Ärene
1988-2004, da vi overvÄket alle de utvalgte koloniene parallelt. Vi har ogsÄ hatt fokus pÄ
sÄrbarhet til enkeltkolonier og beregnet konsekvenser av et eventuelt oljesÞl hvor bestandene
kan bli ytterligere redusert. Som verktĂžy for analysene har vi benyttet levedyktighetsanalyser
(âPopulation viability analysesâ, PVA) som estimerer sannsynligheten for at en bestand skal
kunne overleve i framtida, og ogsÄ klassifisert levedyktigheten til enkeltbestander ved Ä
beregne hvor mange Ă„r det tar fĂžr de eventuelt dĂžr ut. Vi har brukt enkle, tellingsbaserte
modeller, som har som input gjennomsnittlig Ă„rlig vekstrate og variansen i gjennomsnittlige
vekstrater, samt dagens bestandsstĂžrrelse.
Analysene er gjort for seks bestander (kolonier): BjĂžrnĂžya, HornĂžya, HjelmsĂžya, VedĂžy,
Sklinna og Runde. Tre av dem har hatt en entydig negativ bestandsutvikling (HjelmsĂžya,
VedÞy og Runde). Prognoser for levedyktigheten til disse bestandene er dÄrlig. Lavest
levedyktighet har bestanden pÄ VedÞy som har en 50 % sannsynlighet for Ä dÞ ut i lÞpet av
bare 16 Ă„r fram i tid. For HjelmsĂžya og Runde tar det henholdsvis 65 og 56 Ă„r fĂžr bestanden
nÄr en tilsvarende sannsynlighet. Beregnet antall Är til utdÞing for disse tre bestandene er
henholdsvis 70, 124 og 109 Ă„r. Sensitivitetsanalyser viser at disse estimatene for utdĂžing er
lite pÄvirket av variansen i vekstrate, som er det mest usikre estimatet. En reduksjon i
bestandstĂžrrelsen vil imidlertid ha store konsekvenser for levedyktigheten. Spesielt vil
bestanden pÄ VedÞy vÊre ille ute hvis bestanden reduseres ytterligere p.g.a. et oljesÞl.
Kolonien pÄ Sklinna er atypisk i forhold til de andre koloniene. Den har en sterk positiv
bestandsutvikling, men variasjonen i vekstrate fra Är til Är er svÊrt hÞy. Bestanden vil nÄ 30 %
sannsynlighet for Ä dÞ ut fÞrst etter 44 Är. Koloniene pÄ BjÞrnÞya og HornÞya har begge en
positiv vekstrate, og de har sÄ store bestander og liten variasjon i vekstrate at sÄrbarheten til
disse bestandene er svĂŠrt lav. Selv med en halvering av bestandene er det mindre enn 0.001
% sannsynlighet for at de skal dĂž ut i lĂžpet av 30 Ă„r, og estimert tid til utdĂžing er mer enn 1000
Ă„r.
sjÞfugl, lomvi, kolonier, sÄrbarhet, Norskehavet, Barentshavet, seabirds, common guillemot, colonies, population viability, The Norwegian Sea, The Barents Se
Meeting Paris agreement objectives will temper seabird winter distribution shifts in the North Atlantic Ocean
International audienceWe explored the implications of reaching the Paris Agreement Objective of limiting global warming to <2°C for the future winter distribution of the North Atlantic sea-bird community. We predicted and quantified current and future winter habitats of five North Atlantic Ocean seabird species (Alle alle, Fratercula arctica, Uria aalge, Uria lomvia and Rissa tridactyla) using tracking data for ~1500 individuals through resource selection functions based on mechanistic modeling of seabird energy requirements, and a dynamic bioclimate envelope model of seabird prey. Future winter distributions were predicted to shift with climate change, especially when global warming exceed 2°C under a âno mitigationâ scenario, modifying seabird wintering hotspots in the North Atlantic Ocean. Our findings suggest that meeting Paris agreement objectives will limit changes in seabird selected habitat location and size in the North Atlantic Ocean during the 21st century. We thereby provide key information for the design of adaptive marine-protected areas in a changing ocea
Meeting Paris agreement objectives will temper seabird winter distribution shifts in the North Atlantic Ocean
International audienceWe explored the implications of reaching the Paris Agreement Objective of limiting global warming to <2°C for the future winter distribution of the North Atlantic sea-bird community. We predicted and quantified current and future winter habitats of five North Atlantic Ocean seabird species (Alle alle, Fratercula arctica, Uria aalge, Uria lomvia and Rissa tridactyla) using tracking data for ~1500 individuals through resource selection functions based on mechanistic modeling of seabird energy requirements, and a dynamic bioclimate envelope model of seabird prey. Future winter distributions were predicted to shift with climate change, especially when global warming exceed 2°C under a âno mitigationâ scenario, modifying seabird wintering hotspots in the North Atlantic Ocean. Our findings suggest that meeting Paris agreement objectives will limit changes in seabird selected habitat location and size in the North Atlantic Ocean during the 21st century. We thereby provide key information for the design of adaptive marine-protected areas in a changing ocea