Ecosystem effects of sulphur and nitrogen deposition in South Africa:

a view from Europe

Chris CurtisSchool of Geography, Archaeology &

Environmental Studies, Wits

Effects of acid deposition:

Waldsterben

Source: Greenpeace

Free-swimming mayfly Baetis rhodani

Acidification effects in aquatic ecosystems

Brown troutSalmo trutta

Typical softwater plantIsoetes lacustris

DipperCinclus cinclus

Photo:

Nigel Blake

Natterjack toadBufo calamita

Salmo trutta

Critical loadsLinking chemical dose to biological response

Relationship betweenstatus of brown troutpopulations and ANC inNorwegian lakes

Source:Lien, L., Raddum, G.G. , Fjellheim, A.and Henriksen, A. (1996) A critical limitfor acid neutralizing capacity inNorwegian surface waters, based onnew analyses of fish and invertebrateresponses. Sci. Tot. Env. 177, 173-193.ANC is an “index” of acidification damage

Total N dep (2008)from RoTAP (2012)

Critical load exceedance2004-06

not exceeded

2

Exceedancekeq ha-1 year-1

not exceeded

2

not exceeded

2

Exceedancekeq ha-1 year-1

http://www.rotap.ceh.ac.uk/

Nitrate leaching and eutrophication

Empirical critical loads for N

Bobbink & Hettelingh (2011) www.rivm/nl/cce

Critical load exceedances for all ecosystems (2010 deposition)

http://www.emep.int/mscw/mscw_publications.html

EMEP (2012)http://www.emep.int/mscw/mscw_publications.html

Sulphur deposition (mg/m2) in EuropeEMEP (2012)http://www.emep.int/mscw/mscw_publications.html

Europe is a region where deposition is decreasing drastically

Fitted trends in xSO4 deposition at

1988

Source: RoTAP (2012)

Declining sulphur emissions, deposition and surface water sulphate in the UK, 1988-2008

Fitted trends in xSO4 inAWMN sites

Fitted trends in xSO4 deposition at selected ADMN sites

From Defra 20 year report

Curtis & Simpson (in press) Ecological Indicators

eq ha-1a-1

no exceed.< 100100 - 200200 - 500500 - 800

Exceedance of CLs 1980

eq ha-1a-1

no exceed.< 100100 - 200200 - 500500 - 800

Exceedance of CLs GP 2020

Assessment of critical loads of acidity and their exceedances for European lakesCurtis et al. (in press 2013), Springer Environmental Pollution Series

500 - 800800 - 1200> 1200

Dep-data: EMEP/MSC-WCCE

500 - 800800 - 1200> 1200

Dep-data: EMEP/MSC-WCCE

Average annual tropospheric NO2, 2005

Wenig et al. (2008) J. Geophys. Res. 113, D16S45

Acidification in South Africa

Van Tienhoven, A.M., Olbrich, K.A., Skoroszewski, R., Taljaard, J. & Zunckel, M. (1995) Application of the critical loads approach in South Africa. Water, Air & Soil

Pollution 85, 2577-2582.

Water chem not in paper but based on Skoroszewski RW (1995) Sensitivity of surface waters in the Eastern Transvaal Province. CSIR Report WM769.

Net acid deposition in SA

Josipovic et al. (2011) Atmospheric dry and wet deposition of sulphur and nitrogen species and assessment of critical loads of acidic deposition exceedance in South Africa, South African Journal of Science, 107(3/4), Art. #478, 10 pages.

Soil Critical Load exceedance

Acid sensitive waters in SA: upper headwaters & organic acidity

• Suikerbosrand (1992); pH 4.2-6.3 in ephemeral streams after heavy rain (Skoroszewski, RW, 1995, WASP 85: 2331-36)

• Van der Waal (1997) SAJ Aq Sci 23, 42-55; Lake Fundudzi (conifer forested Mutale River pH=5.3, swamp Fundudzi (conifer forested Mutale River pH=5.3, swamp pH 4.1)

• Grobbelaar, J.U. & Stegmann, P. (1987) Water SA 13(3), 151-158; 1970s data from Maluti Mountains, Lesotho –wetland springs (pH 5.3) and streams (pH 5.9) near Letsang la Terae diamond mine; rainfall mean 1975-76 pH of 5.2 (min 3.4)

Verloren Valei Nature Reserve Ramsar wetland,

Mpumalanga

Some wetland streams have pH in range 5.9-6.3;in range 5.9-6.3;

potentially sensitive to acid

deposition

Nitrogen deposition and Biodiversity in South AfricaBiodiversity in South Africa

N Deposition in 2000 & 2030

Bleeker, A., Hicks, W.K., Dentener, F., Galloway, J. and Erisman, J.W., 2011: N deposition as a threat to the world’s protected areas under the Convention on Biological Diversity, Environmental Pollution, 159, 2280-88.

Deposition data from Dentener, F. et al. (2006) Nitrogen and sulfur deposition on regional and global scales: a multimodel evaluation. Global Biogeochemical Cycles 20, 21.

Biodiversity hotspots

Bleeker et al., 2011

Nitrogen depositionto biodiversity hotspots

Phoenix et al (2006)Global Change Biol.12, 470-76.

3: Cape Floristic Region19: Maputaland-Pondoland-Albany29: Succulent Karoo

29

3

19

Mediterranean ecosystems

Critical loads of 3-17 kgN/ha/yr in California (Fenn et al., in press)

N and vegetation

• Western Cape: background dep. c. 2 kgN/ha/yr (Stock & Lewis, 1986, SAJ. Bot. 52, 273-76)

• studies in Cape Metropolitan Area found increasing bryophyte tissue N content in herbarium samples suggesting increase of 6-13 kgN/ha/yrsince 1950 - could lead to critical load exceedance / biodiversity losses (Wilson, Stock & Hedderson, 2009, Env. Poll. 157, 938-45)(Wilson, Stock & Hedderson, 2009, Env. Poll. 157, 938-45)

• Collett et al. (2010) SAJS 106 (5/6) Art.~220; Highveld atmos. nitrogen Ndep 6.7-13.1 kgN/ha/yr

Josipovic et al. (2010) Concentrations, distributions and critical level exceedance assessment of SO2, NO2 and O3 in South Africa. Environ. Monit. Assess. 171, 181-96• CLs for lichens exceeded at 3 Highveld sites and at Elandsfontein only

for forests/semi-natural vegetation

Conclusions1. Unlike Europe, acid deposition is increasing in parts of South Africa2. Deposition loads on Highveld comparable to loads causing acidification of

European soils and waters3. Acidification may be occurring in parts of SA but is probably a highly

localised problem since most of the country is not acid-sensitive4. Nitrogen deposition may be a more insidious and widespread threat than 4. Nitrogen deposition may be a more insidious and widespread threat than

acidification5. N deposition loads on Highveld and in Cape Metropolitan Area are higher

than those found to affect terrestrial vegetation (including Mediterranean types) and surface waters in the northern hemisphere

6. Better data required on national distribution of deposition for both S and N7. Need to investigate the sensitivity of biota to acidity and nutrient nitrogen

effects

Ecosystem effects of sulphur and nitrogen deposition in South Africa: a view from Europe

Chris Curtis, School of Geography, Archaeology & Environmental Studies

KEY QUESTIONS• What is the distribution of wet and dry S and N deposition across South Africa?AcidificationAcidification• How much is known about dose-response functions for acidity and South African biota?

(i.e. are there acid-sensitive species of fish, inverts etc.)?• What is the national distribution of acid sensitive waters? (soils, geology)• Where are critical loads being exceeded at present and in the future?Nutrient N• What are effects of N on sensitive biota? (algae, lichens, higher plants)• Can deposition be an important part of N budgets in certain ecosystems?• What are implications for biogeochemical cycles of excess N deposition? (carbon

sequestration in forests, wetlands; denitrification)

Site June July September

Scoat Tarn P P P

Small Water Co Co Co

Burnmoor Tarn Co N Co

Llyn Edno Co P P

Llyn Gamallt Fawr Co Co N

Llyn Hiraethlyn N N Co

Lochnagar

Eutrophication threat from N deposition

Llyn Hiraethlyn N N Co

Llyn Mair Co P Co

Hammer Pond N Co N

Loch Beanie Co P P

Lochnagar Co P P

Loch Coire nan Eion Co Co P

Loch Coire Fhionnaraich Co N Co

Loch Coire Mhic Fhearchair

Co P P

a) b)

c) d)

Periphytometer testing atRiver Etherow Phytoplankton N and P limitation bioassays

The nitrogen issue: global concern

The Nitrogen Cascade: Galloway et al. (2003), BioScience 53, 341-356.

Future N Deposition

Bleeker et al., 2011