Climate change: potential impacts on marine ecosystems of South Africa and in the Southern Ocean

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1 Climate change: potential impacts on marine ecosystems of South Africa and in the Southern Ocean Presented by: Mr Lucas F. Chauke Dr Azwianewi B. Makhado Dr Jonas Mphepya

2 Coastline stretches more than km from the west by Atlantic Ocean, Indian Ocean (east), and the Southern Ocean (south) contributing to the differing climates experienced in these regions. This makes South Africa s environmental conditions to be characterized by different oceanic dynamics.

3 Ice Plateau at Marion Island Impact of climate change Climate change has been a buzz word for a while but its impact is now noticeable. Climate change is affecting marine ecosystems and is expected to continue to affect fisheries and other ecosystem services

4 Drivers of change Recent changes have been observed in South African marine ecosystems. The main pressures on these ecosystems are fishing, pollution, ocean acidification, habitat alteration and destruction, species invasion. Some of these can be linked to climate change e.g through changes in ocean temperature, chemistry ocean circulation, stratification and nutrient availaibility, eutrophication

5 Global trends in oceans a) Ocean warming Change in temperature of the upper 700 m of the global ocean Source: Intergovernmental Panel on Climate Change Black, red and green curves are from different analyses Grey shading and red and green bars show 90% confidence intervals

6 Global trends in oceans b) Sea level rise The main cause of sea level rise is melt of ice, with heating and expansion of sea water also important Annual averages of global mean sea level Source: Intergovernmental Panel on Climate Change Red reconstructed; blue coastal tide gauge measurements; black satellite altimetry

7 Ocean acidification Ocean acidification refers to the ongoing decrease in the ph of the Earth s oceans, caused by the uptake of anthropogenic carbon dioxide (CO 2 ) from the atmosphere. Between 1751 and 1994 surface ocean ph is estimated to have decreased from approximately 8.25 to 8.14 Present day sea-surface ph (left) and estimated change in sea water ph caused by humancreated CO 2 between the 1700s and the 1990s (right), from the Global Ocean Data Analysis Project and the World Ocean Atlas. The Southern Ocean and the North Atlantic Ocean have experienced high rates of acidification

8 Important regions for top predator breeding in southern Africa There are indications of recent cooling on the West and South coasts and warming on the East Coast over a period of years.

9 The shelf waters slightly further offshore south are slightly warmer, which could be due to the leakage of Agulhas Current and Agulhas Bank water to the Atlantic Ocean

10 Biodiversity indicators Indicators such as the Red List index (based on IUCN red list classifications) have been used internationally to track the conservation status of groups of organisms. The example below (from BirdLife International) shows that globally the conservation status of seabirds deteriorated more rapidly than that of some other groups of birds. South Africa s seabirds (many endemic to southern Africa) are not an exception to this trend two thirds are classified as Threatened or Near Threatened (right) Globally South Africa Critically Endangered Endangered Vulnerable Near Threatened Least Concern

11 Long-term changes in South Africa s marine resources photo C Kearton African Penguins at Dassen Island ca. 1930

12 Major breeding localities of top predators in the Benguela ecosystem

13 Cape fur seal There have been massive changes in distribution in the last 20 years (new colonies etc), population status remained relatively stable, and growth of new colonies have largely compensated for declines at other colonies (e.g. colonies in southern Namibia). And there was also a significant northward shift in the distribution of the breeding population and was extended by ca. 680 km (from Cape Cross to Baia dos Tigres in Angola) whereas the eastward range of the breeding population remained constant throughout the time series. The potential availability of prey such as horse mackerel Trachurus trachurus capensis for top predators may have influenced such distribution

14 Proportion w Cape Agulhas Proportion w Cape Agulhas Closed ,0 Anchovy 0,8 0,6 0,4 0,2 0,0 South-east displacement of forage fish species In the 1990s, adult stocks of South Africa s two most important forage fish species shifted their distributions from the west coast to being mostly east of Cape Agulhas. The northernmost fish processing plant at Lambert s Bay was closed in ,0 0,8 0,6 0,4 0,2 0,0 Sardine

15 Seabird responses to changes in the distributions of some prey species Thousand pairs Thousand pairs Thousand pairs Thousand pairs Thousand pairs Thousand pairs Thousand pairs Thousand pairs Large decreases for species that compete with fisheries for prey but have inflexible diets and are unable to adapt locations of breeding Increases for species that compete with fisheries for prey but have flexible diets or are able to adapt their localities of breeding Stability for species that do not competing with fisheries for prey African Penguin Cape Gannet Crowned Cormorant , ,5 1,0 0, , Cape Cormorant Swift Tern White-breasted Cormorant , ,5 5 2,5 1,00 0,75 0,50 0, , Bank Cormorant Roseate Tern 2 1,5 1 0,5 0,15 0,10 0, ,

16 Roy et al. 2007

17 Long-term change at sub-antarctic Marion Island

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19 Temperature trends in the sub-antarctic region Marion Island shows the strongest warming trend (0.21 o C per decade, R 2 = 0.55) Individual station data from these locations thus appear representative for larger regional trends

20 1994/ / / / / / / / / /13 Pairs Inshore-breeding seabirds Numbers of Crozet Shags (left) and Gentoo Penguins (right) breeding at Marion Island have shown similar decreasing trends both are benthic feeders eating similar prey. The congruent trends suggest possible ongoing change in the benthic marine environment. Regionally the Crozet Shag is Critically Endangered and the Gentoo Penguin is Endangered Gentoo Penguin Crozet Shag

21 1994/ / / / / / / / / / / / / / / / / / / /13 Thousand pairs Thousand pairs Crested penguins Numbers of both species of crested penguin breeding at Marion Island have decreased the Southern Rockhopper Penguin is regionally Endangered; the Macaroni Penguin is Vulnerable Macaroni Penguin Southern Rockhoper Penguin

22 Southern Rockhopper Penguin Mass of Southern Rockhopper Penguins returning to breed from overwintering grounds (where they spend six months) has decreased: a) males, b) females. This was not the case for Macaroni Penguins, for which disease at large colonies contributed to decreases

23 Overwintering distributions of crested penguins in the South Indian Ocean (collaboration with France) Macaroni (red and pink lines), Southern Rockhopper (yellow and white) and Northern Rockhopper (green) Penguins. Locations: Marion (circle), Crozet (triangle), Kerguelen (lozenge) and Amsterdam (square) islands. Macaroni and Southern Rockhopper Penguins at island groups have different winter feeding grounds

24 Divergent trends of Phoebetria albatrosses At the Prince Edward Islands Sooty Albatross has decreased, Light-mantled Albatross has increased Light-mantled Albatross Marion: + 6% p.a. since 1996 Sooty Albatross Marion: 2% p.a. since 1996

25 At sea distributions of Phoebetria albatrosses Proportion Sooty Albatrosses have a more northerly at-sea distribution than Light-mantled Albatrosses, which makes them more susceptible to by-catch mortality in long-line fisheries that operate in the south Indian and Atlantic Oceans and off South Africa. This probably resulted in the divergent trends of the two species 0,12 Positions at sea for birds from Prince Edward Islands 0,10 0,08 0,06 0,04 0,02 0, Degrees S Sooty Albatross Light-mantled Albatross

26 Spatial management of oceans expected to play an important role in biodiversity conservation The Prince Edward Islands Marine Protected Area was proclaimed in April 2013 Controlled zone light grey; restricted zones dark grey

27 In the Southern Hemisphere, there have been poleward shifts and local declines for ice-dependent populations of Adélie Penguins breeding in the West Antarctic Peninsula but increases and a southward range extension of Gentoo Penguins, which do not depend on ice It has been predicted that all colonies of Emperor Penguins north of S could be lost when Earth's tropospheric temperature reaches 2 C above pre-industrial levels, with negative impacts on all colonies north of 70 S.

28 Population of elephant seal has not increased despite ceasation of sealing. In the southern ocean, seals dived to deeper depths when foraging in warmer waters. Results from time-at-depth indices showed that both male and female seals spent less time at targeted dive depths in warmer water, and were presumably less successful foragers when diving in warmer water. Continued warming of the Southern Ocean may result in the distribution of prey for southern elephant seals shifting either poleward and/or to increasing depths, presumably increasing energy utilization while searching for prey.

29 Ecosystem resilience ongoing contributions are made to global research aimed at determining thresholds for ecosystem resilience e.g. across a wide variety of species and ecosystems for which longterm data were available (including South Africa) seabird breeding success consistently decreased and became more variable when prey abundance fell below one-third of its maximum observed value

30 We have not inherited this earth from our forefathers but borrowed it from future generations Ancient proverb

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