Joseph Holden @ University of Leeds
Abstract:
Global wetlands store way more carbon than tropical forests yet they are under threat from human action. Degradation of peatlands alone is estimated to contribute 5 % of all global anthropogenic CO 2 emissions each year. Therein lies the opportunity. If we can protect and restore wetlands we can not only reduce losses of carbon to the atmosphere, but we can also generate net carbon uptake from the atmosphere. Wetland restoration can also generate a number of other societal co-benefits that can be associated with financial incentives and investment returns.
However, there are a number of challenges to mapping and quantifying carbon stores, net greenhouse gas exchange and ecosystem service benefits that would enable the necessary validation that may be required for some green financing investments. In this presentation we will discuss some of the modelling and data opportunities that could be advanced to address those challenges.
Bio:
Professor Holden is a Cambridge University graduate and holds a PhD from Durham University, UK. He is a Fellow of the UK’s Royal Geographical Society and Fellow of the UK’s Royal Meteorological Society. He has held the Chair of Physical Geography at the University of Leeds for the last 15 years during which time he has been the Research Dean for the Faculty of Environment and he is also Director of water@leeds, one of the largest interdisciplinary university-based water research centres in the world. He has expertise in the hydrology and carbon dynamics of wetlands, river basin hydrology and land management impacts on flooding, soil processes and flowpaths. He won the Gordon Warwick Medal from the British Society for Geomorphology and also the Leverhulme Prize, both for compelling evidence of his outstanding research achievements. He is also the Champion for the national Freshwater Quality Research Programme in the UK. He has published > 200 papers and is editor of leading undergraduate textbooks on water (Holden, J. (2020) (ed) Water Resources: an integrated approach, 2 nd edition. Routledge) and on physical geography (Holden, J. (ed) An Introduction to Physical Geography and the Environment. 4 th edition. Pearson Education, 2019). Professor Holden has supervised >30 PhD students, and delivered > 100 funded research projects.
Summary:
Global wetland maps have high uncertainty
Topographic wetland index
Estimates wetness based on where water should flow
Big discrepancies between different index variants
Peatlands
Wetlands where organic matter decays and then drops deeper under layers of more organic matter
Relatively less water flow than other wetlands so organic matter keeps accumulating
50% of peat solid matter is carbon, so its a major sink for carbon emissions
PEATMAP
Map of peatlands, which are carbon rich
2.84% of land area / 4.23 million km2
We don’t know how deep the carbon stores in peatlands is
Remote sensing doesn’t measure peatland depth well
Significant amounts of peatland has been lost over time
Due to draining, farming, etc.
E.g. in UK its been 15-20 feet over 150 years.
Worse in the tropics, where reductions in the water table (e.g. because of irrigation ditches) can quickly decompose the peat; this can cause all peatland in a region to be lost in 10 years
This carbon has been released into the atmosphere
~5% of all anthropogenic emissions is from peatland (CO2 and methane)
The physical models of carbon accumulation are reasonably known
Water-table position (dry soil causes degradation)
Temperature (decomposition of plant matter)
Plant community (a few species are key to peatland health)
DigiBog: simulates peat growth and decay over decades to millennia
Digibog-Hydro: integrates landscape and water management
INCA-C model: daily time series of soil organic carbon Dissolved Organic Carbon (DOC)
Can drive it with land use and climate scenarios
Threats to wetlands
Agriculture (biggest threat)
Drainage
Extraction
Plantation forestry
Fire
Pollution/overgrazing
Human infrastructure
Water obstruction
Dynamics of emissions from peatlands
Used eddy covariance sensors
If system too dry or too wet, then petland emits
If water table is ~5-10 cm below surface, peatland sequesters carbon
More general wetlands have similar sweet spot
They developed high quality wetland maps: 10m resolution wetland map for Africa
Estimating water table remotely using ENVISAT-ASAR C-Band backscatter
Error is +=1 meter
But sweet spot for wetland sequestration is ~10cm
Applying Random Forest models to data brings error to ~30cm
PeatDataHub: combining global peatland datasets (https://peatdatahub.net/)
Bigger picture of the dynamics (working to create comprehensive model)
Overall flow:
Anthropogenic drivers
Drivers proxies (wetland measurements)
Ecosystem functions and indicators
Social value of wetlands
Collecting existing datasets from prior research
Training statistical models of individual processes in the flow
Long-term goal is to create process-based models of each process
Co-benefits of investing in wetlands
Carbon / GHGs
Flood risk reduction
Coastal protection
Downstream water quality
Biodiversity net gain
Productivity
Land value and environmental payments
Financial investments system requires quality and assurance
Requires effective measurement and modeling
Water table is an easy proxy for estimating wetland health without measuring gas emissions
Big opportunity of connection environmental analytic services to the finance sector
Reinsurance sector is heavily regulated, depends on clear records of risk
Need to have models that predict the impact of wetland treatments on outcomes
A collection of petland emissions data can have a business model for risk management and modeling
Model uncertainty is still too high to be useful for use in lawsuits but there are some limited scenarios where confidence can be tight