Tree tops

Fire occurrence rates in the Amazon have increased in 59% of areas with reduced deforestation and risks cancelling part of the carbon savings achieved by UN measures to reduce greenhouse gas emissions from deforestation according to research to Dr Luiz Aragao.

Dr Luiz Aragao was awarded a NERC Urgency grant of £65,000 to investigate the impacts of forest fires on carbon stocks during the 2010 drought in Amazonia.

Landscape and ecosystem dynamics

Tropical forest productivity and change

Major advances have been made in quantifying tropical forest productivity and change. Through NERC funding, highly-cited research has demonstrated increased fire events in Amazonia despite declining deforestation, shown the impacts of the 2005 Amazonian drought on carbon emissions, and that changed radiation from aerosol pollution was a stimulant of global plant production and carbon sequestration. Our research has also informed decision makers on Amazon forest degradation, and resulted in ground-breaking, and very highly cited work on terrestrial carbon dynamics across multiple biomes.

Research group members are involved in a diverse range of research activities in tropical forests, from detailed in situ measurements, through to remote sensing and large-scale modelling. Field measurements have focused on quantifying the carbon budget of tropical rainforests to understand main drivers of its spatial and temporal variability. Measurements have been conducted in several parts of the Amazon basin as part of the efforts to establish a large-scale plot-based monitoring network to quantify the impacts of forest disturbance in the carbon cycle of Amazonian forests. We led the establishment of experimental field sites to evaluate the long-term effect of forest fires in tropical forest productivity and functioning by using a detail bottom-up approach linking classic field ecology methods and CO2 efflux measurements from forest components. This research was funded by NERC in collaboration with several Brazilian Universities and Institutions.

Our remote sensing research focuses on three main topics, exploring the potential of large-scale satellite information for (i) understating the spatial variability of biophysical variables in tropical forest canopies, (ii) mapping forest disturbance, (iii) quantifying phenological cycles in tropical forests and its relationships with environmental variables. This research is based mainly on data from the Moderate Resolution Imaging Spectroradiometer (MODIS) and several other satellite-derived products including: Shuttle Radar Topography Mission, Tropical Rainfall Measuring Mission, INPE/GL1.2 global radiation dataset, INPE/PRODES gross deforestation dataset, JRC Land cover map of South America, AVHRR and MODIS active fire products. Most of our work is coupled with field investigations in the Amazon basin. We have strong collaborative links with the Brazilian Institute of Space Research (INPE) and the NASA-Jet Propulsion Laboratory.

Interdisciplinary research focuses on the quantifying the interactions between climate, human activities and ecosystem ecology in order to understand large-scale effects of  human-induced climate and environmental change on the tropical forest biome and to explore mitigation and adaptation strategies to inform governments and policymakers. Currently, our work is centred on exploring the effects of climate and human activities on fire incidence and carbon emissions in Amazonia and on understanding how this influences the implementation of UN-led international mitigation policies such as Reducing Emissions from Deforestation and Degradation (REDD) in this region. Most of our work is carried out in the Brazilian Amazon but we are keen to expand our studies to other tropical countries, and have done so recently in Colombia. We seek to understand how environmental changes may affect the earth system functioning and how socio-economic measurements, such as payments for maintaining carbon stocks and environmental services in tropical countries, may mitigate global climate change and protect tropical ecosystems to support the sustainable development of the rainforest nations.

Our empirical research is complemented with extensive expertise in modeling vegetation, biogeochemical cycles, the impact of historical and future scenarios of LULCC on climate and climate-chemistry-ecosystems interactions, with a strong focus on tropical ecosystems. We also co-ordinate international multi-model studies on the contribution of terrestrial ecosystems to the global carbon cycle, and are at the forefront of model evaluation, inter-comparison and benchmarking. The group is a the forefront of developments in the Joint UK Land Environment Simulator, JULES, the land component of the Hadley Centre climate model, with theme leaders in plant physiology (Dr. Mercado) and vegetation dynamics and disturbance (Prof. Sitch), tasked with coordinating the wider academic community developments in these fields. Members of the group currently lead an undergraduate field course to Brazil each year.

News stories:

Fires in Amazon challenge emission reduction programme
Geography academic awarded NERC grant to examine drought in Amazonia

Recent funding:

1/11/2013 – 31/10/2017
EU FP7 I (€472,213 to UoExe) Land-use change: assessing the net climate forcing, and options for climate change mitigation and adaptation” Co-Is Sitch, Friedlingstein (Exeter)

01/09/2012 – 31/08/2016
Consortium NERC Grant (£444,573 to UoExe;) SAMBBA, South American Biomass Burning Analysis, PI – James Haywood (CEMPS), Co-Is – Sitch, Mercado (CLES)

17/11/2012- 16/10/2016
Standard NERC Grant (£152,978.00 to UoExe). Understanding How Drought Affects the Risk of Increased Mortality in Tropical Rain Forests, PI - Meir (Edinburgh), CoIs - Mencuccini (Edinburgh) and Sitch (Exeter), Project Partner, Chris Jones, Met Office

Jan 2012-2015
NERC CASE Studentship, Impact of tropospheric O3 on crop production under future climate and atmospheric CO2 concentrations, and their interactions within the Earth System, University Supervisors, Stephen Sitch, Peter Cox, Case Partner: Met Office Hadley Centre (Jemma Gornall)

Key publications

  1. Sitch, S. et al., (2013) Trends and drivers of the regional-scale sources and sinks of carbon dioxide over the past two decades, Biogeosciences Discussions, submitted
  2. Huntingford, C., Zelazowski, P. et al. inc. Mercado, L. M., Sitch, S. (2013). Simulated resilience of tropical rainforests to CO2-induced climate change. Nature Geoscience 6, 268-273.
  3. Saatchi, S., Asefi-Najafabady, S. et al. inc. Aragão, L. E. O. C. (2013). Persistent effects of a severe drought on Amazonian forest canopy. Proceedings of the National Academy of Sciences of the United States of America 110, 565-570.
  4. ter Steege, H., Pitman, N. C. A. et al. inc. Feldpausch, T. R. (2013). Hyperdominance in the Amazonian Tree Flora. Science 342, 325-+.
  5. Wang, W., Ciais, P. et al. inc. Sitch, S. (2013). Variations in atmospheric CO2 growth rates coupled with tropical temperature. Proceedings of the National Academy of Sciences of the United States of America 110, 13061-13066.
  6. Ainsworth, E. A., Yendrek, C. R., Sitch, S.  et al. (2012). The Effects of Tropospheric Ozone on Net Primary Productivity and Implications for Climate Change. Annual Review of Plant Biology 63, 637-661.
  7. Aragão, L. E. O. C. (2012). ENVIRONMENTAL SCIENCE The rainforest's water pump. Nature 489, 217-218.
  8. Booth, B. B. B., Jones, C. D. et al. inc. Sitch, S. (2012). High sensitivity of future global warming to land carbon cycle processes. Environmental Research Letters 7, 024002.
  9. Fauset, S., Baker, T. R. et al. inc. Feldpausch, T. R. (2012). Drought-induced shifts in the floristic and functional composition of tropical forests in Ghana. Ecology Letters 15, 1120-1129.
  10. Feldpausch, T. R., Lloyd, J. et al. (2012). Tree height integrated into pantropical forest biomass estimates. Biogeosciences 9, 3381-3403.
  11. Feldpausch, T. R., Banin, L. et al. (2011). Height-diameter allometry of tropical forest trees. Biogeosciences 8, 1081-1106.
  12. Mercado LM, Lloyd J, Dolman AJ, Sitch S., Patino, S. (2011) Modelling basin-wide variations in Amazon forest productivity - Part 1: Model calibration, evaluation and upscaling functions for canopy photosynthesis), Biogeosciences, 8(3), 653-656
  13. Mercado, L. M., Patino, S. et al. (2011). Variations in Amazon forest productivity correlated with foliar nutrients and modelled rates of photosynthetic carbon supply. Philosophical Transactions of the Royal Society B-Biological Sciences 366, 3316-3329.
  14. Pan, Y., Birdsey, R. A. et al. inc. Sitch, S. (2011). A Large and Persistent Carbon Sink in the World's Forests. Science 333, 988-993.
  15. Zelazowski, P., Y. Malhi, C. Huntingford, S .Sitch, JB Fisher (2011) Changes in the potential distribution of humid tropical forests on a warmer planet, Phil Trans Roy Soc A, 369 (1934), 137-160.
  16. Galbraith, D., P. E. Levy, S. Sitch, et al. (2010) Multiple mechanisms of Amazonian Forest biomass losses in three Dynamic Global Vegetation Models under climate change, New Phytologist, 187(3), 647-665
  17. Aragão, L. E. O. C. and Shimabukuro Y. E. (2010). The Incidence of Fire in Amazonian Forests with Implications for REDD. Science 328, 1275-1278.
  18. Doherty, R. M., Sitch, S. et al. (2010). Implications of future climate and atmospheric CO2 content for regional biogeochemistry, biogeography and ecosystem services across East Africa. Global Change Biology 16, 617-640.
  19. Girardin, C. A. J., Malhi, Y., Aragão, L. E. O. C.  et al. (2010). Net primary productivity allocation and cycling of carbon along a tropical forest elevational transect in the Peruvian Andes. Global Change Biology 16, 3176-3192.
  20. Aragão, L.E.O.C. et al. (2009) Above- and below-ground net primary productivity across ten Amazonian forests on contrasting soils, Biogeosciences 6, 2759-2778.
  21. Fyllas, N. M., Patino, S. et al. inc. Mercado, L. M. (2009). Basin-wide variations in foliar properties of Amazonian forest: phylogeny, soils and climate. Biogeosciences 6, 2677-2708.
  22. Le Quere, C., Raupach, M. R. et al. inc. Sitch, S. (2009). Trends in the sources and sinks of carbon dioxide. Nature Geoscience 2, 831-836.
  23. Lewis, S. L., Lloyd, J. et al. inc. Sitch, S. (2009). Changing Ecology of Tropical Forests: Evidence and Drivers. Annual Review of Ecology Evolution and Systematics. 40, 529-549.
  24. Lewis, S. L., Lopez-Gonzalez, G. et al. inc. Feldpausch, T. R. (2009). Increasing carbon storage in intact African tropical forests. Nature 457, 1003-U3.
  25. Malhi, Y., Aragão, L. E. O. C. et al. (2009). Exploring the likelihood and mechanism of a climate-change-induced dieback of the Amazon rainforest. Proceedings of the National Academy of Sciences of the United States of America 106, 20610-20615.
  26. Mercado, L. M., Bellouin, N. et al. (2009). Impact of changes in diffuse radiation on the global land carbon sink. Nature 458, 1014-U87.
  27. Phillips, O. L., Aragão, L. E. O. C. et al. (2009). Drought Sensitivity of the Amazon Rainforest. Science 323, 1344-1347.
  28. Piao, S., Fang, J. et al. inc. Sitch, S. (2009). The carbon balance of terrestrial ecosystems in China. Nature 458, 1009-U82.
  29. Sitch, S., Huntingford, C. et al. (2008). Evaluation of the terrestrial carbon cycle, future plant geography and climate-carbon cycle feedbacks using five Dynamic Global Vegetation Models (DGVMs). Global Change Biology 14, 2015-2039.
  30. Sitch, S.,et al. (2005). Impacts of future land cover on atmospheric CO2 and climate. Global Biogeochemical Cycles, 19, GB2013, doi:10.1029/2004GB002311