Dr Anna Harper
EPSRC LWEC Research Fellow, Proleptic Lecturer in Climate Science
Telephone: 01392 724588
Extension: (Streatham) 4588
I am interested in the role of vegetation in climate change, and the role of land-atmosphere interactions in current and future climate. There are many interesting questions to answer: How will forests respond to climate change? Will the land surface continue to be a carbon sink? What land management practices can contribute to reducing greenhouse gases in the atmosphere? Are there feedbacks from the way vegetation responds to climate change that we need to consider? Below are some of the topics I'm currently researching:
Land-based climate mitigation and negative emissions
Our recent work can be found in Nature Communications: Land-use emissions play a critical role in land-based mitigation for Paris climate targets.
The Paris Climate Agreement set an ambition of limiting climate change to well below 2°C warming since pre-industrial times (mid-19th century), with efforts to limit warming to 1.5°C. But at current rates of emission, it will take less than a decade to emit the carbon required to get to 1.5°C of warming.
So what can we do? We can and should cut emissions, but we should also investigate strategies for removing CO2 from the atmosphere and their implications for ecosystems and people. One option is to produce bioenergy from plants (like switchgrass or wood pellets) at power stations equipped for Carbon Capture and Storage (CCS), which store CO2 in geologic reservoirs instead of emitting it back into the atmosphere. This is called bioenergy with CCS (or BECCS). Another option is to regrow forests, or to avoid future deforestation. Both of these strategies require large land areas to make a dent in climate change, and they have knock-on effects on food, energy, water, and natural ecosystems.
My current research investigates the potential for negative emissions of CO2 using BECCS and forest management, and the impacts on food, energy, water, and natural ecosystems. By quantifying both the mitigation potential and the impacts, we aim to assess various scenarios for reducing climate change and their consequences.
My research group uses the land surface model JULES to study biogeochemical cycles, vegetation and carbon cycle dynamics, and will be using the UK Earth System Model to study the effects of climate change on bioenergy production and forests, as well as the impacts on climate of large-scale land use change for bioenergy and carbon sequestration.
My work is funded by an EPSRC Living With Environmental Change fellowship (2016-2019), the NERC grants "Climate, Land-Use, and Ecosystem Services for 1.5C", and "Feasibility of Afforestation and Biomass energy with carbon capture and storage for Greenhouse Gas Removal (FAB-GGR)".
I've been involved in a few other interesting studies relating to the Paris Agreement:
Collins WJ, et al. (2018) Increased importance of methane reduction for a 1.5 degree target, Environmental Research Letters*
Comyn-Platt E, et al. (2018) Carbon budgets for 1.5 and 2C targets lowered by natural wetland and permafrost feedbacks, Nature Geosciences
And I've contributed to policy-relevant summaries of mitigation pathways for Paris, led by the EU CRESCENDO project.
The global carbon budget
Some of my work the land surface model JULES has contributed to the Global Carbon Project. I've worked on improving vegetation dynamics in the model, as summarized in these two model development papers:
Harper AB et al. (2018) Vegetation distribution and terrestrial carbon cycle in a carbon cycle configuration of JULES4.6 with new plant functional types, Geoscientific Model Development
Harper AB et al. (2016) Improved representation of plant functional types and physiology in the Joint UK Land Environment Simulator (JULES v4.2) using plant trait information, Geoscientific Model Development*
Plants "eat" CO2 to live, so to first order vegetation will benefit from growing atmospheric CO2 concentrations. In reality, there are several complicating factors which will control how much extra CO2 plants can assimilate: changes in weather and climate patterns, changes in nutrient availability, and human land use change and degradation. I'm involved in a project to better understand how plants will respond to rising CO2 using "FACE" (free-air enrichment of CO2) experiments. During these experiments, extra CO2 is pumped into a study area and the responses of the plants and soils are measured. My role is to use JULES to see which processes might be most important in the real world that are missing in earth system models. There is an exciting new FACE project at the University of Birmingham, BiFor FACE. There are two publications so far from this work:
Ryan EM et al. (2017) Gross primary production responses to warming, elevated CO2 , and irrigation: quantifying the drivers of ecosystem physiology in a semiarid grassland, Global Change Biology*
De Kauwe M et al. (2017) Challenging terrestrial biosphere models with data from the long-term multi-factor Prairie Heating and CO2 Enrichment experiment Global Change Biology
I am particularly interested in the Amazon rainforest, an amazing ecosystem which provides invaluable services to humanity - not least of which is the storage of CO2. Drought threatens this ecosystem. How the forest responds to droughts and the likelihood of future droughts will both play large roles in the future of the global carbon cycle and climate. My PhD research focused on the implications of forest drought responses for the climate system.
Harper AB, et al. (2010), Role of deep soil moisture in modulating climate in the Amazon forest. Geophysical Research Letters.
Harper AB, et al. (2014) Impact of evapotranspiration on dry season climate in the Amazon forest. Journal of Climate. Press release: http://www.exeter.ac.uk/news/featurednews/title_334187_en.html
This is a good overview of climate thresholds that includes some discussion of the fate of the Amazon forest:
Good P, et al (2018) Recent progress in understanding climate thresholds: Ice sheets, the Atlantic meridional overturning circulation, tropical forests and responses to ocean acidification, Progress in Physical Geography, volume 42, no. 1, pages 24-60, DOI:10.1177/0309133317751843.
*PDF available on publication page