Grassland Soil Carbon Stocks: Status, Opportunities and Vulnerability What do we know?

1. Grassland Soil Carbon Stocks: Status, Opportunities and Vulnerability Grassland Soil Carbon Stocks: Status, Opportunities and VulnerabilityWhat do we know? Richard Conant Natural Resource Ecology Laboratory & School of Global Environmental Sustainability Colorado State University Institute for Sustainable Resources Queensland University of Technology

2. CO2 concentrations are increasing: • Human activities are driving increases in atmospheric CO2 2007 IPCC AR4: effects of warming evident; cost of reducing emissions far less than damage they will cause 1995 IPCC 2nd report: “signature of human activities” 1956 Phillips: 1st somewhat realistic global climate model 1897 Chamberlin: model of global C exchange 1938 Callendar: CO2 greenhouse global warming is underway 1896 Arrhenius: 1st calculation of anthropogenic global warming 1988 IPCC established; 1st report 1990 1976 Deforestation recognized as important driver of climate change 1859Tyndall: some gasses absorb IR; could drive climate change 1930s Global warming trend since late 19th century reported 1958 Keeling: Atm. CO2 measurements begin at Mauna Loa

3. Perspective • Climate policy timeline 2008-2012: 1st Kyoto compliance period A modest proposal? Near-term implementation of a global policy that affects all parts of everyone’s lives. 2005: Kyoto into effect 2001: Marrakech accords 1997: Kyoto Protocol 1992: US Energy policy act; incl. Section 1605(b) 1992: Rio Treaty – establishes UNFCCC

5. Carbon flow in grassland ecosystems • What do we know? • Carbon flow in grassland ecosystems • The things we do on the land impact carbon stocks • Grazing intensity/seasonality • Species composition • Soil fertility • Other factors influence carbon stocks • Climate • Soil characteristics • Past land use • Given information about these things, soil carbon stocks can be predicted • Current stocks • gains or losses w/ changes in management CO2 livestock respiration Forage consumption Soil carbon Stocks

6. Carbon stocks in grassland ecosystems • What do we know? --management influences C stocks Sequestration potential = f(C loss) System carbon Disturbance Management change Time

7. Carbon flow in grassland ecosystems • What do we know? • Carbon flow in grassland ecosystems Some numbers: 5.1Bha  730Mha converted to cropland ~415Pg C (in top 20cm)  ~at least 30 PgC lost due to conversion to cropland

8. (Glasod database; Oldeman 1994)

9. (Conant and Paustian 2002)

10. Carbon stocks in grassland ecosystems • What do we know? --management influences C stocks (Conant et al. 2001)

11. Carbon stocks in grassland ecosystems • What do we know? --technical potential for sequestration is large

12. Carbon stocks in grassland ecosystems • What do we know? • Grassland soil C stocks are substantial. • Management impacts carbon stocks – C stocks are susceptible to loss • Carbon lost from grassland systems can be re-gained through changes in management • Improved management practices can increase soil carbon stocks • Technical potential for sequestration in grasslands is large

13. Grassland Soil Carbon Stocks: Status, Opportunities and Vulnerability Grassland Soil Carbon Stocks: Status, Opportunities and VulnerabilityWhat don’t we know? • Richard Conant • Natural Resource Ecology Laboratory & • School of Global Environmental Sustainability • Colorado State University • Institute for Sustainable Resources • Queensland University of Technology

14. Carbon stocks in grassland ecosystems • What do we know? --measurements on the ground are sparse • Data are very sparse globally. (Conant and Paustian 2002)

15. Carbon stocks in grassland ecosystems • What do we know? --measurements on the ground are sparse • Data are very sparse globally. • We measure soil C stock changes (either before/after or neighboring fields)

16. Carbon stocks in grassland ecosystems • What do we know? --management influences C stocks System carbon Disturbance Now Management change The future Time

17. Carbon stocks in grassland ecosystems • What do we know? --measurements on the ground are sparse • Data are very sparse globally. • We measure soil C stock changes (either before/after or neighboring fields) • This approach is uncertain and has limitations • One way forward: more data, better models, tighter data-model linkages.

18. Carbon stocks in grassland ecosystems • What don’t we know? • 1. We still have limited information on how management influences C stocks • We have a growing database of on-the-ground studies • Data are still limited • Little consistency between sources • Synthesis still challenging

21. Carbon stocks in grassland ecosystems • What don’t we know? • Data on the ground are sparse • We still have limited information on how management influences C stocks • Few studies focus on mechanisms driving changes in C stocks • Current models have limited capability to represent observed C stock changes. • This inability to understand drivers of change limits our ability to forecast C stock changes.

22. Carbon stocks in grassland ecosystems • What do we know? --management influences C stocks Sequestration potential = f(C loss) Sequestration potential = f(C loss, propensity for C gain) System carbon Disturbance Management change Time

23. Carbon stocks in grassland ecosystems • What don’t we know? -- unknown capacity to change management (IPCC AR4 CH8)

24. Carbon stocks in grassland ecosystems • What don’t we know? • Data on the ground are sparse • We still have limited information on how management influences C stocks • We don’t know how widely practices that sequester carbon can/will be implemented • Technical potential differs from – and is easier to assess than – economic potential • Technical potential is just one piece of the equation • Activity and economic data are limited in the US, but much (MUCH!) more-so world-wide

25. Food production is part of the C cycle human respiration CO2 livestock respiration Forage consumption How does harvesting biomass affect ecosystem carbon stocks? Are there ways to maximize both harvest and ecosystem carbon stocks? Soil carbon Stocks

26. Carbon stocks in grassland ecosystems • What don’t we know? -- limited knowledge about costs/benefits

27. Carbon stocks in grassland ecosystems • What don’t we know? • Data on the ground are sparse • We still have limited information on how management influences C stocks • How widely practices that sequester carbon can/will be implemented; limited information about costs vs. benefits • Impacts of carbon-sequestering practices on other greenhouse gas emissions • Upstream – energy use, inputs • Downstream – transport, CH4 emissions

28. Carbon stocks in grassland ecosystems • Some recommendations • Expand on-the-ground data collection, greater focus on understanding mechanisms • Coordinate data collection and release to lower barriers to meaningful synthesis • Take a systems perspective; understand sequestration within the larger context of economic costs and benefits