Post on 08-Sep-2018
Ecology for a small planet
Prof Bob Scholes Inaugural lecture
21 June 2016
• Picture of an elephant eating a tree, with other herbivore present
What does that ecologist see in
me?
A Systems Ecologist’s view of the world
Very Large Plant-Eater
Plants that VLPE eats +
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+
Plants VLPE doesn’t eat
Other plant-eaters
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+
-
- -
What happens if I give the system a shove here?
Solving an old puzzle Why is some veld ‘sweet’ and some ‘sour?’
‘Sweetveld’ and ‘sourveld’ are not properties of the species,
but a property of the system!
Cold, wet, infertile places
Hot, dry, fertile places
%N too low to digest in winter
%N above threshold all
year
Generate and keep more N
Time of year spring winter summer
0.5
% N
in g
rass
digestion threshold in ruminants
Retain relatively more carbon than
nitrogen N leak from fire & denitritfication
Biological Nitrogen Fixation
Blackmore A.C., M.T. Mentis & R.J. Scholes. 1990. The origin and extent of nutrient rich patches in a nutrient poor savanna. Journal of Biogeography 17, 463-470.
Ellery, W., M.C. Scholes & R.J. Scholes. 1995. The distribution of sweetveld and sourveld in South Africa’s grassland biome in relation to environmental factors. African Journal of Range and Forage Science 12, 38-45
Three things that interest me
• Biogeochemistry, especially of carbon
• Earth Observation, especially putting it together
• Ecosystem dynamics, especially at the edge
The common thread is taking ecology to big scales
Is that 2 ½ things to many?
A salutary experience
… but the flow in the river is only 20 x 106m3/y !
NA
SA
Botany Hons Field Trip, July 1978
Calculation of transpiration by trees in the Kuiseb river, by scaling up from leaf measurements
Picture of Jane and porometer
Gobabeb
Rossing
Multiplied by Explanation Yields
0.3 g/m2Leaf/s Acacia transpiration rate
22.9 m2/m2 Leaf area per stem XS area 6.87 g/m2stem/s
0.001 m2/m2 Rooted fraction in riparian belt 0.01 g/s/m2ground
100 m Mean width of riparian 0.69 g/s/river
440000 m Length of riparian 3.02E+05 g/s/river
3.15E-05 s/y seconds per year; g per 106m3 9.54 x 106m3/y
Where did we go wrong? …we neglected the interactions!
Leaflet
Branch
Canopy
Landscape
advection, partioning
root and canopy
resistance
humidity
Jarvis PG, McNaughton KG. 1986. Stomatal control of transpiration: scaling up from leaf to region. Advances in Ecological Research, 15(1): 49.
Incr
eas
ing
scal
e
xylem resistance
Is big ecology just little ecology
with lots of zeros?
Scholes, R.J. & B.H. Walker.1993. An African savanna: synthesis of the Nyslvley study. Cambridge University Press, Cambridge
Prentice, I.C…, R.J. Scholes et al. 2001. The carbon cycle and atmospheric carbon dioxide. Third Assessment Report of the Intergovernmental Panel on Climate Change, WG1. Cambridge University Press, Cambridge. 1(3):183-237. Falkowski, P., R.J. Scholes,..et al. 2000. The global carbon cycle: a test of our knowledge of earth as a system. Science 290, 291-296.
1015 g/0.51x 1015m2 100 g/m2
Scaling up through ‘paint-by-numbers’ Map ecosystems, assign a mean value to each, multiply by area and add up
my bit!
But ecosystems are not internally homogeneous! You can do better by replacing the classes with a continuous function
Scholes, R.J., J. Kendall & C.O. Justice. 1996. The quantity of biomass burned in southern Africa. Journal of Geophysical Research 101: 23667-76. Scholes, R.J., C.O. Justice & D. Ward. 1996. Emissions of trace gases and aerosol particles due to vegetation burning in southern-hemisphere Africa. Journal of Geophysical Research 101: 23677-23682.
Scholes et al 1996 500 Gg CH4/y
Hao et al (1990) 4163 Gg CH4/y
Fire-related greenhouse gas emissions from Africa south of the equator
Pyrogenic emission = area burned* fuel load * combustion fraction * emission factor
The carbon stock of South Africa A recent example of continuous field modelling
https://www.environment.gov.za/sacarbonsinkatlas Based on Scholes et al 2014 National Terrestrial Sink Assessment. CSIR for DEA.
A better way: measure the phenomenon at its actual scale
Stömmel diagram
Vance, T and R Doel 2010 Graphical Methods and Cold War Scientific Practice: The Stommel Diagram’s Intriguing Journey from the Physical to the Biological Environmental Sciences . In: Historical Studies in the Natural Sciences (DOI: 10.1525/hsns.2010.40.1.1.) Scholes et al 2013 Multiscale and cross-scale assessments of social ecological systems and the their services COSUST 5:1-10
Measuring carbon exchange at the leaf scale
Infrared gas analyser and leaf chamber
Scholes, R.J., P. R. Dowty, K. Caylor , D.A.B. Parsons, P.G.H. Frost and H.H. Shugart 2002 Trends in savanna structure and composition on an aridity gradient in the Kalahari. Journal of Vegetation Science 13, 419-428.
Measuring carbon exchange at the landscape scale
Stömmel diagram
Scholes, R.J., et al. 2001. The environment and vegetation of the flux measurement site near Skukuza, Kruger National Park. Koedoe 44(1), 73-83. Archibald, S. and R.J. Scholes.2007. Leaf green-up in a semi-arid African savanna – separating tree and grass responses to environmental cues. Journal of Vegetation Science 18, 583-594. Kutsch, W.L., N. Hanan, R.J. Scholes, I. McHugh, W. Kubheka, H. Eckhardt, C. Williams. 2008. Response of carbon fluxes to water relations in a savanna ecosystem in South Africa. Biogeosciences 5, 1797-1808.
Measuring carbon exchange at the Africa scale
Valentini, R., Arneth, A., Bombelli, A., Castaldi, S., Cazzolla Gatti, R., Chevallier, F., ... & Scholes, R. J. (2014). A full greenhouse gases budget of Africa: synthesis, uncertainties, and vulnerabilities. Biogeosciences, 11, 381-407. Nickless, A., Ziehn, T., Rayner, P. J., Scholes, R. J., & Engelbrecht, F. (2014). Greenhouse gas network design using backward Lagrangian particle dispersion modelling–Part 2: Sensitivity analyses and South African test case. Atmospheric Chemistry and Physics Discussions, 14(8), 11301-11342.
Southern Africa in a test-tube: the SAFARI 2000 campaign
Annegarn, H.J., L. Otter, R.J. Swap and R.J. Scholes. 2002. Southern Africa’s ecosystem in a test-tube; a perspective on the Southern African Regional Science Initiative (SAFARI 2000). South African Journal of Science 98, 111-113.
Scholes, R.J., G. M. Mace, W. Turner, G. N. Geller, N. Jürgens, A. Larigauderie, D. Muchoney, B. A. Walther and H. A. Mooney. 2008. Toward a Global Biodiversity Observing System. Science 321, 1044-1045. Fritz, S., R.J. Scholes, M.Obersteiner , J. Bouma and B. Reyers. 2008. A conceptual framework for assessment of the benefits of a Global Earth Observation System of Systems. IEEE Systems Journal, 2(3), 338-348. Scholes, R.J., P.M.S. Monteiro, C.L. Sabine and J.G. Canadel. 2009. Systematic long-term observations of the global carbon cycle. Trends in Ecology and Evolution. 24, 427-430. Verstraete, M.M., … R.J. Scholes, et al. 2010. Towards a Global Drylands Observing System: Observational Requirements and Institutional Solutions. Land Degradation & Development DOI: 10.1002/ldr.1046 (15 pp) Scholes, R.J., et al 2012. Building a global observing system for biodiversity. Current Opinion in Environmental Sustainability 2012, 4:1–8.
Taking the pulse of the planet
GEOBON
Can we usefully measure biodiversity loss? How many variables do you need?
Scholes, R.J. and R. Biggs.2005. A biodiversity intactness index. Nature 434, 45-49. Biggs, R., B. Reyers and RJ Scholes. 2006 . A biodiversity score for South Africa. South African Journal of Science, 102, 277-283. Pereira, H.M., …Scholes et al 2013. Essential Biodiversity Variables for Global Earth Observation. Science 339,277 – 278.
The Biodiversity Intactness Index and Essential Biodiversity Variables
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An evolving science-policy interface observing, evaluating, acting
2000
2010
1990
Ozone Assessment
IPCC 3AR Lead Author
Synthesis Author
IPCC 4AR Lead Author
IPCC 5AR Convening Lead
Synthesis author
IPCC
Millenium Assessment WG Co-chair
Land Degradation
Co chair
IPBES formed
2020
1980
GCOS
GTOS chair
IGBP -DIS
Glo
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bse
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Sy
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of
Syst
ems
des
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Bio
div
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ork
ch
air
Observation systems Assessment systems
Elephant Leader
Shale Gas Co-leader
…and in South Africa
Stability in savannas
Scholes, RJ & S. Archer. 1997. Tree-grass interactions in savannas. Annual Review of Ecology and Systematics 28, 517-44. Scholes RJ 2003 Convex relationships in ecosystems containing trees and grass. Environment and Resource Economics 26, 559-574
…more on savanna dynamics
The Walter Hypothesis is inadequate to explain savannas
Multiple stable states are ubiquitous
There are lots of ways to get a stable outcome: picking one is hard!
Equilibrium and disequilibrium models are not mutually exclusive
Sankaran, M…, R.J. Scholes, et al 2005. Determinants of woody cover in African savannas. Nature 438, 846-849. Vezzoli, R., C. De Michele, H. Pavlopoulos and R.J. Scholes. 2008. Dryland ecosystems: the coupled stochastic dynamics of soil water and vegetation and the role of rainfall seasonality. Physical Review E, 77 (5) DOI: 10.1103/PhysRevE.77.051908 De Michele., R. Vezzoli, H. Pavlopoulos, and R.J. Scholes . 2008. A minimal model of soil water –vegetation interactions forced by stochastic rainfall in water-limited ecosystems. Ecological Modelling, 212 (3-4), 397-407. Accatino, F, C. DeMichele, R.Vezzoli, D. Donzelli, R.J. Scholes. 2010. Tree–grass co-existence in savanna: Interactions of rain and fire. Journal of Theoretical Biology, 267, 235–242. DeMichele, C., F.Accatino, R.Vezzoli, and R.J.Scholes. 2011. Savanna domain in the herbivores-fire parameter space exploiting a tree–grass–soil water dynamic model. Journal of Theoretical Biology 289 74–82. Donzelli, D., C. De Michele, R.J. Scholes. 2013. Competition between trees and grasses for both soil water and mineral nitrogen in dry savannas. Journal of Theoretical Biology 332 181–190.
Stability and resilience at the global scale
Neufeldt, H.; …Scholes, R….; 2013. Beyond climate-smart agriculture: toward safe operating spaces for global food systems. Agriculture & Food Security, 2:12. Mace, G M.,…, Robert J. Scholes, et al. 2014. Approaches to defining a planetary boundary for biodiversity. Global Environmental Change 28 : 289-297.
An accidental scientist Complex nonlinear systems as a metaphor for Life
Lucky birth
Game Ranger
Biologist
Local scale
Clipboard & binoculars
Pure scientist
Researcher Worked for a scientist
Systems ecology
Inspiring lecturer
Earth System Science
IGBP GCTE
Earth Observation
Adopted by NASA
Science-policy
IPCC & MEA
Two paths diverged in a wood, and I – I took the one less travelled by
And that has made all the difference. Robert Frost
Bob.Scholes@wits.ac.za