Impacts of climate change on biological systems

1. Impacts of climate change on biological systems David B. Lobell dlobell@stanford.edu Outline: Some Basic Principles Observed Impacts Projected impacts Several slides taken from NAS report on stabilization targets http://dels.nas.edu/Materials/Presentations/Stabilization-Targets

2. Plants grow better in higher CO2 Photosynthesis: CO2 + H20  sugar + O2

3. Plants grow better in higher CO2 Photosynthesis: CO2 + H20  sugar + O2 Water use efficiency:

4. Measuring the CO2 fertilization effect FACE: Free-air CO2 enrichment (Long et al. 2006)

5. Plants usually grow worse in higher temperatures The main effects of warming: -faster rates of development (see below) -faster rates of photosynthesis and respiration -higher rates of evapotranspiration (important in dry regions) -fewer frosts (important in cold regions) “birth” “adolescensce” “adulthood” “death” In a cooler year, this process can take ~10 days longer than in warmer year, which means 10 or more days to photosynthesize

6. An example: California Almonds

7. Animal impacts Food sources changing in quantity, quality, and composition Many animals affected by loss of sea and land ice Migratory animals affected by change in seasons

8. Observed Impacts (not easy to “observe” impacts)

9. Option 1: show a big co-incidence of climate and biological changes

10. Option 1: show a big co-incidence of climate and biological changes ELAINE: Well, I mean, he was in the apartment, and then it's gone and it's in your apartment. RAVA: Maybe you think we're in cahoots. ELAINE: No, no.. but it is quite a coincidence. RAVA: Yes, that's all, a coincidence! ELAINE: A big coincidence. RAVA: Not a big coincidence. A coincidence! ELAINE: No, that's a big coincidence. RAVA: That's what a coincidence is! There are no small coincidences and big coincidences! ELAINE: No, there are degrees of coincidences. RAVA: No, there are only coincidences! ..Ask anyone! http://www.seinfeldscripts.com/TheStatue.htm

11. Option 2: run a model with and without observed climate changes

12. % Yield Impact

14. Projected Impacts

15. Recent and Future CO2 levels A2 A1b 2 x pre-industrial B1

16. Projections for average global temperatures IPCC, 2007

17. Average climate model projections of soil moisture change by 2080 IPCC, 2007

18. Food: Large potential decreases in certain crops and locations

19. Wildfire in the western US(1-2°C warming) Western US

20. Ocean Acidification and Corals Photo courtesy of Ove Hoegh-Guldberg Global coral reef distribution and biological production of calcium carbonate skeleton (shell material) taking into account both ocean acidification and thermal bleaching 20

22. And there are also unquantified risks…. 22

23. Can’t separate “biological” and “human” responses to climate change • Farmers and scientists are not dumb • In response to these pressures, people are likely to adapt. • Two main types of adaptations • Trade • Management or genetic changes

24. Human responses to climate change • Trade Cool nations “win” Warm nations “lose” One example of estimated impacts for 2x CO2 (from Cline 2007)

25. Summary • Higher CO2 generally helps (except for C4 plants in moist areas) • Warming generally hurts (except where its very cold) • Precipitation changes are small at global scale, but could be important in some places • There are various forms of evidence for observing impacts, none of them perfect • Projections tend to focus on things we understand pretty well, but there are lots of things that could change that we can’t really quantify (e.g., what are the impacts of climate change on national security?) • For human systems (e.g., agriculture) understanding adaptation is important

26. Human responses to climate change 2) Management changes Red = no management changes Green = “adaptation” IPCC, 2007

27. Direct effects of climate change -So warming can have some positive and some negative effects. -The net balance differs depending on crop and location -Overall, crops in most regions prefer cooler temperatures Average Global Yields vs. temperatures, 1961-2002 Yield Change (%) Temperature Change (ºC)