Environmental Change

Past climate dynamics

Past climate change in Africa

Sub-Saharan Africa is one of the most climatically sensitive areas on Earth, varying from lake-studded savannah woodland to hyperarid desert over the course of a glacial-interglacial cycle. To understand these great fluctuations we are looking at geomorphic records of climate change from the extremes; interglacial and glacial periods. We have documented evidence that the White Nile River valley once hosted a very large freshwater lake with a probable surface area of around 45,000 km2, making it one of the largest lakes in the world at the time. The lake owes its existence to much higher precipitation due to a more intense summer monsoon. In Ethiopia and the Drakensburg Mountains in Lesotho and South Africa we are studying evidence of glaciation to document the timing and magnitude of cooling during the height of the last ice age.

Key publications:

Barrows, T. T. Williams, M. A.J., Mills, S. C., Duller, G. A.T., Fifield, L. K. Haberlah, D. Tims, S. G. and Williams, FM. (2014). A White Nile megalake during the last interglacial period. Geology, 42, 163-166, DOI: 10.1130/G35238.1

Williams, M.A.J., Williams, F.M., Duller, G.A.T., Munro, R.N., El Tom, O.A.M., Barrows, T.T., Macklin, M., Woodward, J., Talbot, M.R., Haberlah, D., Fluin, J., (2010) Late Quaternary floods and droughts in the Nile valley, Sudan: new evidence from optically stimulated luminescence and AMS radiocarbon dating. Quaternary Science Reviews 29, 1116-1137.

Recent grants:

Mills, S. C. and Barrows, T. T. The impact of the Agulhas Current on the Ice Age climate of the Drakensberg Mountains, South Africa. Royal Geographical Society, Peter Fleming Award (£9,000)

Past climate change in South-West China

With more then 60% of the world’s population living in areas affected by the Asian Monsoon understanding the degree of variability within the system is critical if we are to successfully militate against the impact of future climatic change. Lake sediment archives offer a unique opportunity to study regional scale climate dynamics and how significant climatic changes in the past have impacted terrestrial systems. We are currently focusing on lake records in south-western China most notably Sichuan and Yunnan provinces, where significant changes in the regional climate are predicted for the future.  Using a range of multi-proxy techniques we are examining the occurrence and impact of rapid climate change over centennial- millennial timescales.

Key publications:

Cook, C and Jones, R. T.  (2012). Palaeoclimate dynamics in continental Southeast Asia over the last ~ 30,000 Cal yrs BP. Palaeogeography, Palaeoclimatology, Palaeoecology, 339–341, 1–11, ,DOI:10.1016/j.palaeo.2012.03.025

Recent grants:

Quantification of the impact of climate change on landscape evolution as mediated by plant community dynamics: Lake Mugecuo , Sichuan, BGS (£56,000)

Past climate change in New Zealand

The last glacial period can provide valuable insights into the mechanisms of rapid and extreme climatic and environmental change. Unfortunately, although there are numerous ice, marine and terrestrial records from around the world that span this period, precise comparisons are hampered by the absence of a robust terrestrial calibration before 12,410 years ago. Here we will exploit a unique but fast disappearing resource in New Zealand to derive a decadally-resolved tree-ring record of changing atmospheric radiocarbon content during periods of known extreme climatic and environmental change thereby allowing us to test hypotheses of global synchroneity.

Recent grants:

Towards a Decadally-Resolved Radiocarbon Calibration for the Last Glacial Period (30,000-11,700 years ago) Using New Zealand Kauri (Agathis australis). NERC £290,333.89. NE/H009922/1.

Unique slices of time: Salvaging New Zealand sub-fossil kauri (Agathis australis) that span the termination of the Last Glacial Period. NERC Urgency Award £26709.00 2010, NE/I007660/1.

Environmental sustainability in Southern India: Suranga Water harvesting

Suranga are a traditional water control technology found in districts of Karnataka and Kerala states in India that are threatened by population increase, resource depletion and climate change. Surangas are rapidly being abandoned in favour of modern well systems, the sustainability of which is questionable as local hydrological systems adjust to changing patterns of water use and availability. This study seeks to measure the sustainability of suranga and evaluate its role in reducing vulnerability to periodic water shortage and promoting community resilience.

Recent grants:

Sustainability of Suranga Technology in South Karnataka and North Kerala States of India (PI Crook U.Hertfordshire)

Palaeoenvironmental history of biodiversity hotspots in South America

Areas of exceptional biodiversity face the dual challenge of direct human modifications of the landscape, coupled with the effects of human-induced climate change. While tropical ecosystems have been forced to accommodate prior environmental change, it has been suggested that modern rates of change are so rapid that they could result in extinction events. Palaeoecological evidence shows that the influence of human occupation (Urrego et al 2013) coupled with Holocene climatic variability caused the highest rates of ecological change in western Amazonia during the past 46,000 years (Urrego et al 2010). The modern speed of climatic changes are however greater than any experienced by these forests over the Late Pleistocene and Holocene, and foresee unprecedented changes.

Key publications:

Urrego, D.H., Bush, M.B., Silman, M.R., Niccum, B.A., De La Rosa, P., McMichael, C., Hagen, S., Palace, M., 2013. Holocene fires, forest stability and human occupation in southwestern Amazonia. Journal of Biogeography 40, 521-533.

Urrego, D.H., Bush, M.B., Silman, M.R., 2010. A long history of cloud and forest migration from Lake Consuelo, Peru. Quaternary Research 73, 364-373.

Palaeoclimate of southern Africa

The study of Earth’s past is particularly important for our understanding of present-day global warming. All components of the Earth’s system are interconnected, and changes occurring in one region often have consequences in another, hence the importance of understanding the system as a whole. Southern Africa is a climatically sensitive area where the amount of warm waters flowing from the Indian to the Atlantic Ocean can modify ocean circulation and in turn global temperatures. Research in the region shows that fire activity in southern Africa is orbitally driven and opposite to that observed in the northern hemisphere (Daniau et al 2013), and that aridity increased during the warmest periods of the last interglacial (Urrego et al 2013).

Key publications:

Urrego, D.H., Sánchez Goñi, M.F., Daniau, A.-L., Lechevrel, S., Hanquiez, V., 2013. Increased aridity in southwestern Africa during the last-interglacial warmest periods. Climate of the Past Discussions 9, 4323-4363.

Daniau, A.-L., Sánchez Goñi, M.F., Martinez, P., Urrego, D.H., Bout-Roumazeilles, V., Desprat, S., Marlon, J.R., 2013. Orbital-scale climate forcing of grassland burning in southern Africa. Proceedings of the National Academy of Sciences 110, 5069–5073.

Palaeoecological evidence for climate and environmental change

This research topic focuses on determining palaeoecological evidence for climate and environmental change, especially over the Holocene, concentrating on Iceland, Western Ireland and SW England. This uses a range of proxies recovered from lake sediments and peat deposits, but especially concentrating on pollen and chironomids to develop palaeoclimatic records. The research uses pollen modelling techniques to develop more meaningful reconstructions of past vegetation cover as it impacts on early communities. Climate data from the past is used to assess projections of future climate change and especially how such projections can be effectively communicated.

Key publications:

Caseldine CJ  2012. ‘Concepts of time in (Paleo-)Science and some implications’. WiRES Climate Change, 3, 329-338.

Langdon PG, Caseldine CJ, Crowdace IW, Jarvis S, Wastegard S, Crowford TC. 2011 ‘A chironomid-based reconstruction of summer temperatures in NW Iceland,’ Quaternary Research, 75, 451-460.

Fyfe R, Caseldine C, Gillings M 2010 ‘Pushing the boundaries of data? Issues in the construction of rich visual past landscapes’, Quaternary International, 220, 153-159.

Recent funding:

£48,420.45  Natural England (co-applicant I.Maclean) “Palaeoecological evidence to inform identification of potential climate change refugia and areas for ecological restoration”

Peatlands and the global carbon cycle using observations and models

Peatland ecosystems hold very large amounts of carbon, accounting for at least a third of all global soil carbon. Understanding the dynamics of carbon and especially the way in which it is may be lost following human or natural disturbance is important to be able to predict feedbacks to future climate change. A recent research focus is on developing carbon inventories and assessing carbon accumulation rates and losses in relation to climate variability and disturbance. A recently completed project funded by a consortium including the Duchy of Cornwall Estate, Natural England, the National Trust and Dartmoor National Park Authority developed estimates of carbon stocks and accumulation rates for Dartmoor. A  NERC funded project is now investigating changes in global peat accumulation rates over the last 1000 years and the development of models to simulate the contribution of peatlands to the global carbon cycle. Finally, we are also working on an interdisciplinary project under the NERC Arctic Programme to understand the consequences of permafrost melting for carbon storage in arctic peatlands and soils.

Key publications:

Charman, D.J., Beilman, D. W., Blaauw, M., Booth, R. K., Brewer, S., Chambers, F. M., Christen, J. A., Gallego-Sala, A.,, et al. (2013) Climate-driven changes in peatland carbon accumulation during the last millennium. Biogeosciences, 10, 929-944.

Parry, L. E., Charman, D. J., Noades, J. P. (2012). Methods for modelling peat depth in blanket peatlands. Soil Use and Management, 28, 614-624.

Billett M.F., Charman D.J., Clark J.M., Evans C.D., Evans M.G., Ostle N.J., Worrall F.,  Burden A., Dinsmore K.J., Jones T., McNamara N.P., Parry L., Rowson J.G., Rose, R. (2010). Carbon balance of UK peatlands: current state of knowledge and future research challenges. Climate Research 45, 13-29.

Leifeld, J., Gallego-Sala, A. V. & Steffens, M. 2012. Sensitivity of peatland carbon loss to organic matter quality. Geophysical Research Letters, 39, L14704. doi:10.1029/2012GL051856

Loisel, J., Gallego-Sala, A. V. & Yu, Z. 2012. Global-scale pattern of peatland Sphagnum growth driven by photosynthetically active radiation and growing season length. Biogeosciences, 9, 2737-2746.

Recent funding:

2012-2015 Carbon Cycling Linkages of Permafrost Systems (CYCLOPS). NERC Arctic Programme NE/K000179/1. (with collaborators from Edinburgh, Sheffield and Sussex Universities).

2011-2014 Joint PhD Studentship with UQAM, Quebec. Carbon cycling in Northern peatlands and feedbacks to climate change.

2011-2015 Peatlands and the global carbon cycle during the past millennium: a global assessment using observations and models. NERC NE/I012915/1. 

2007-2010 Policy and practice for sustainable carbon management of moorlands. Duchy of Cornwall, Natural England, National Trust, Dartmoor National Park and Great Western Research.

Reconstruction of past climate variability from peatlands

Reconstructing past climate variability is important in understanding natural climate dynamics as a context for future change. Past hydrological variability is particularly complicated to reconstruct because of regional and seasonal changes over time. Peatlands hold detailed records of past climate change as they accumulate steadily over millennia and contain well-preserved records in the peat. We have focused especially on using a group of microfossils (testate amoebae) to reconstruct change, and compiling multiple records to establish a more robust picture of hydrological variability over different spatial scales.  Further development work on multi-proxy and stable isotope records is now underway to extend the application of this approach.

Key publications:

Charman, D.J. (2010). Centennial climate variability in the British Isles during the mid-late Holocene. Quaternary Science Reviews, 29, 1539-1554.

Charman, D.J., Barber, K.E., Blaauw, M., Langdon, P.G., Mauquoy, D.M., Daley, T.J., Hughes, P.D.M. and Karofeld, E. (2009) Climate drivers for peatland palaeoclimate records. Quaternary Science Reviews, 28, 1811-1819. DOI: 10.1016/j.quascirev.2009.05.013.

Amesbury, M., Mallon, G., Charman, D.J., Hughes, P.D.M., Booth, R. K., Daley, T., Garneau, M. (2013). Statistical validation of a new testate amoeba based transfer function for water-table depth reconstruction on ombrotrophic peatlands in north-eastern Canada and Maine, United States. Journal of Quaternary Science, 28, 27-39.

Recent funding:

2009-2013 Holocene Land-Ocean-Atmosphere Interactions on the Eastern Seaboard of North America. NERC Standard Grant NE/G020272/1. (with collaborators from Southampton and Swansea)