Ecosystem change in the southern Benguela and the underlying processes

Blamey, Laura K.; Shannon, Lynne J.; Bolton, John J.; Crawford, Robert J. M.; Dufois, François; Evers-King, Hayley; Griffiths, Charles L.; Hutchings, L.; Jarre, Astrid; Rouault, Mathieu; Watermeyer, Katherine; Winker, Henning

doi:10.1016/j.jmarsys.2014.11.006

Cited by 111 publications

(84 citation statements)

References 143 publications

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“…Off South Africa, the distributions of anchovy, sardine and rock lobster shifted south and east during the 1990s and early 2000s (Blamey et al, 2015). Similarly, for each of the four seabirds that feed mainly on anchovy and sardine, there were large recent decreases in the proportions of birds breeding off northwest South Africa (Northern Cape and north Western Cape) in the 1990s and/or 2000s (Figure 2; Crawford et al, 2014b).…”

Section: Discussionmentioning

confidence: 92%

“…Off South Africa, in the southern Benguela ecosystem there have been recent changes in the distributions and population sizes of several animals, including seabirds (e.g., Whittington, 2004;Crawford et al, 2007Crawford et al, , 2014bKirkman et al, 2012;Crawford, 2013) and three forage species that are important prey for seabirds: anchovy (Engraulis encrasicolus), sardine (Sardinops sagax) and rock lobster (Jasus lalandii) Blamey et al, 2015). From 1984 to 1995 most (61 ± 21% by mass standard deviation) spawning anchovy were located west of Cape Agulhas (Figure 1), whereas from 1996 to 2005 this proportion halved to 31 ± 11% (information in Roy et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

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A changing distribution of seabirds in South Africaâ€”the possible impact of climate and its consequences

et al. 2015

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In the southern Benguela ecosystem off South Africa, there were recent shifts to the south and east in the distributions of three forage resources (anchovy, sardine, rock lobster), which probably were influenced by environmental change although fishing too may have played a part. In this study, we review information on trends in distributions and numbers of eight seabirds breeding in South Africa. For five species that feed predominantly on anchovy, sardine or rock lobster, their populations off northwest South Africa decreased markedly. For three of these species, which exhibit behavioral inertia and have restricted foraging ranges when breeding (African penguin, Cape cormorant, bank cormorant), there were large decreases in their overall populations in South Africa. Conversely, for two showing more plasticity and able to range over wide areas or move between breeding localities (Cape gannet, swift tern) there were increases. It is thought that movement of forage resources away from the northern islands led to a mismatch in the distributions of breeding localities and prey of dependent seabirds off western South Africa and to attempts by several species to establish colonies on the southern mainland closer to food resources. There also were shifts to the south and east in the distributions of three seabirds that do not compete with fisheries for prey (crowned cormorant, white-breasted cormorant, kelp gull), suggesting some environmental forcing, but decreases of these species off northwest South Africa were less severe and populations in South Africa remained stable or increased in the long term. It is likely, because many fishing plants are located in the northwest, that there was increased competition between seabirds and fisheries for prey as forage resources moved south and east. Potential interventions to mitigate the adverse impacts of distributional changes for seabirds include allocations of allowable catches of shared forage resources at regional levels, closures to fishing around impacted seabird colonies and establishment of new colonies nearer to the present location of food.

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Section: Discussionmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

A changing distribution of seabirds in South Africaâ€”the possible impact of climate and its consequences

et al. 2015

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“…Kelp forest declines have now been documented in many regions in response to a variety of stressors (18,(31)(32)(33)(34)(35), but kelp abundances have been stable or increasing in other areas (17,36,37). Here, we amass a global database of kelp abundances to provide a comprehensive picture of kelp forest change.…”

Section: Significancementioning

confidence: 99%

Global patterns of kelp forest change over the past half-century

Krumhansl

Okamoto

Rassweiler

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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546

515

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Kelp forests (Order Laminariales) form key biogenic habitats in coastal regions of temperate and Arctic seas worldwide, providing ecosystem services valued in the range of billions of dollars annually. Although local evidence suggests that kelp forests are increasingly threatened by a variety of stressors, no comprehensive global analysis of change in kelp abundances currently exists.Here, we build and analyze a global database of kelp time series spanning the past half-century to assess regional and global trends in kelp abundances. We detected a high degree of geographic variation in trends, with regional variability in the direction and magnitude of change far exceeding a small global average decline (instantaneous rate of change = −0.018 y −1 ). Our analysis identified declines in 38% of ecoregions for which there are data (−0.015 to −0.18 y −1 ), increases in 27% of ecoregions (0.015 to 0.11 y −1 ), and no detectable change in 35% of ecoregions. These spatially variable trajectories reflected regional differences in the drivers of change, uncertainty in some regions owing to poor spatial and temporal data coverage, and the dynamic nature of kelp populations. We conclude that although global drivers could be affecting kelp forests at multiple scales, local stressors and regional variation in the effects of these drivers dominate kelp dynamics, in contrast to many other marine and terrestrial foundation species. A ssessing ecosystem change on a global scale has been instrumental in highlighting the magnitude of human impacts on natural ecosystems. For example, awareness of global declines in fish populations (1), coral reefs (2), and tropical rainforests (3) has substantially increased public interest and subsequent political motivation for environmental conservation. In some cases, global assessments have highlighted complex patterns of change (4, 5), which often reflect variable trajectories among regions (4). SignificanceKelp forests support diverse and productive ecological communities throughout temperate and arctic regions worldwide, providing numerous ecosystem services to humans. Literature suggests that kelp forests are increasingly threatened by a variety of human impacts, including climate change, overfishing, and direct harvest. We provide the first globally comprehensive analysis of kelp forest change over the past 50 y, identifying a high degree of variation in the magnitude and direction of change across the geographic range of kelps. These results suggest region-specific responses to global change, with local drivers playing an important role in driving patterns of kelp abundance. Increased monitoring aimed at understanding regional kelp forest dynamics is likely to prove most effective for the adaptive management of these important ecosystems.

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“…The longterm sustainability of this strategy is questioned as intensified effort may impact the biophysical environment negatively as a result of increased fishing pressure on already fully-or over-exploited stocks. 27,32 It is not easy to attribute definitive reasons for diversification and restructuring taking place in the Mossel Bay linefishery. Sufficient capital was required for these craft fishers to diversify.…”

Section: Migrate (Temporarily) 12%mentioning

confidence: 99%

“…This boat-based, multi-user and multi-area fishery exploits 50 commercially important fish species across South Africa. 26,27 A variety of anthropogenic stressors including resource scarcity, poor socio-economic conditions and policy and regulatory challenges affect the inshore social-ecological system of the area. These stressors make small-scale commercial fishers and their communities increasingly vulnerable to local and global changes.…”

Section: Introductionmentioning

confidence: 99%

case study from the southern Cape linefishery 2: Considering one’s options when the fish leave

Gammage¹,

Jarre²,

Mather³

2017

S. Afr. J. Sci.

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Fishers in the small-scale, commercial linefishery in the southern Cape, South Africa, are exposed to variability and change in the marine social-ecological system of which they are a part. Faced with multi-scalar changes within this complex system, fishers employ a wide range of strategies in reaction to change. As part of a broader study of stressors that bring about change in these systems, this contribution examines the fishers’ responses to these changes and is based on a participant-led, semi-structured interview process of skippers/boat owners, crew, processors and spouses/partners, in six communities in the southern Cape region, and has been supplemented with appropriate secondary data. The results are discussed using a resilience framework. The data were initially considered thematically by stressor, but results identified that a place-based analysis was equally important. Three major groupings were identified: (1) fishers who adapt and show clear business-orientation, (2) fishers who cope, and (3) fishers who react and are thus caught in a poverty trap. In addition to place-specific history, local feedback loops and indirect effects need to be better accounted for to understand these responses to change at various scales. The results of this study are expected to contribute to the basis of scenario planning in the region.

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Ecosystem change in the southern Benguela and the underlying processes

Cited by 111 publications

References 143 publications

A changing distribution of seabirds in South Africaâ€”the possible impact of climate and its consequences

A changing distribution of seabirds in South Africaâ€”the possible impact of climate and its consequences

Global patterns of kelp forest change over the past half-century

case study from the southern Cape linefishery 2: Considering one’s options when the fish leave

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