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Dr Amanda Thomson, NERC Centre for Ecology & Hydrology

National Environmental Statistics Advisory Committee Autumn Meeting – Wednesday 28th November 2012

An introduction to the LULUCF sector in the national Greenhouse Gas Inventory

Presentation overview

• An introduction to greenhouse gas (GHG) inventories

• The Land Use, Land Use Change and Forestry (LULUCF) sector

• Calculating net emissions• Forestry• Land Use Change• Land Management

• Related research and developments

• Questions

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Why do we need them?

Because we need to measure progress towards national and international GHG reduction targets

An introduction to greenhouse gas inventories

NATIONAL GHG INVENTORIES

What is an inventory?• Not just a list!• Detailed year-on-year assessment

of national GHG emissions• Made up of a complex linked

database & models• Follows international protocols &

audit to allow inter-national comparison

Energy

Agriculture

Industrial Processes

Solvents

Waste

Land Use, Land Use Change

and ForestryNATIONAL

GHGINVENTORY

ANNUAL PUBLICATIONS

International and national submissions:• UN Framework Convention on Climate Change• UK and Devolved Administration climate change targets

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The Land Use, Land Use Change and Forestry (LULUCF) sector

What is LULUCF ?

Land Use, Land Use Change and Forestry• Covers anthropogenic GHG emissions and uptake by

vegetation and soil– Changes in carbon stocks (carbon dioxide

(CO2)emissions by sources and removals by sinks)

– Emissions of GHGs by sources: CO2, methane (CH4) , nitrous oxide (N2O)

• Only sector that can have a potential carbon sink• Inventory consists of annually-updated values for each

year between 1990 and current year (2010)

LAND USE CATEGORIES

• All land in a country must be assigned to one of these categories

• Land use areas are compiled from multiple sources:

• Forestry Commission• Countryside Survey• Agricultural statistics• Other government

statistics

Scottish net LULUCF emissions 1990-2010

CEH and LULUCF

• CEH has led the compilation of LULUCF inventories since the mid-1990s

• Each year we produce:• Annual inventories for the UK, England, Scotland,

Wales and Northern Ireland and the UK’s Overseas Territories and Crown Dependencies

• Projections of emission scenarios to 2050• Breakdowns of the latest inventory numbers by

Local Authority• Advice on the LULUCF sector and science for policy

makers and international negotiations

Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug

Inventory data for UK, OT/CDs, completed CRF tables

DECC emission statistics published

National inventory report (2 chapters and annex)

Devolved administration GHG inventory report

Devolved administration LULUCF report and numbers

Maps of LULUCF emissions and report

Projections of LULUCF emissions to 2050

UNFCCC submission with UK and OT/CD numbers

EU submission with UK numbers

UNFCCC synthesis and assessment report review

EC consistency report checks

UNFCCC Expert Review

UK internal review (numbers and report text)Revi

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Reporting Schedule

Methodology overview

• Have to follow Good Practice Guidance laid down by Intergovernmental Panel on Climate Change (IPCC)

– Transparent, consistent, comparable and accurate

• IPCC provide default methods and emission factors (GHG emitted per unit area) but it is good practice to develop country-specific methods and data

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Carbon stock changes in vegetation and soils and greenhouse gas emissions from forest management

Calculating emissions: Forestry

Sector category Details

Carbon stock changes in vegetation and soils

Uses forest carbon accounting model, C-Flow, based on UK-specific parameters, management practices and planting activity data

Direct N2O emissions from nitrogen fertilization

Uses subset of planting activity data, country-specific fertilizer application rate and IPCC default N2O emission factor

Non-CO2 emissions from drainage

N2O emissions from forest drainage will be included in the 1990-2011 inventory

Biomass burning (controlled and wildfres)

Uses country-specific activity data and biomass densities, and IPCC default emission ratios

Harvested Wood Products

Uses forest carbon accounting model, C-Flow, based on UK-specific parameters, management practices and planting activity data

Forest activities producing GHG emissions

FOREST MANAGEMENT: PLANTING

• Forest area inventories occur at irregular intervals in the UK

• UK woodland area at 31 March 2011:

• 3.1 Mha (56% conifers) (2010 NFI) vs.

• 2.9 Mha estimated from 1995-99 NIWT adjusted for new planting

• c. 68% of UK woodland area have been planted since 1950

• Forestry Commission production planning uses area and Yield Class models rather than frequent inventory

• Annual planting data is comprehensive (available since 1921)

Age profile of woodland in Scotland(adapted from 1995-99 National Inventory of Woodland and Trees)

FOREST MANAGEMENT ACTIVITY DATA• Area of new forest planting provided annually by the Forestry

Commission (split by conifer/broadleaf and FC/privately-managed)• All broadleaf planting assumed to be on mineral soils• Conifer planting split between mineral and organic soils on country-specific

basis• Adjusted for deforestation losses• Split between

• Forests established prior to 1920 assumed to have zero net carbon flux• Forests established 1921- fluxes modelled with C-Flow

• C-Flow model calculates the net change in pools of carbon in standing trees, litter and soil in conifer and broadleaf forests and in products

FOREST CARBON FLOWS IN THE C-FLOW MODELAtmospheric CO2

Woodybiomass

Non-woodybiomass

Woodylitter

Non-woodylitter

Soil organicmatter

Woodproducts

Product decay

Stemthinning

andharvesting

Transfer ofresidues to soil

Soil decomposition

Natural mortalityThinningsHarvest debris

Photosynthesis (NPP)(from volume growth curve & expansion factors)

Woody litter decayNon-woody litter

decay

C-FLOW POST-MODEL PROCESSING

• Allocation of Land converted to Forest between Cropland/Grassland/Settlements based on proportional allocation in Countryside Survey data

• Adjustment of Forest carbon stock changes for deforestation using original implied carbon stock changes (Mg C/ha) and adjusted areas

HARVESTED WOOD PRODUCTS

• Timber is added to the harvested wood products pool from• Harvesting and thinning under standard forest management• Timber produced from deforestation

• 5% of living biomass transferred to litter and soil pools at felling• Residence times (time of 95% of C to be lost) of wood products

depend on type and origin of products and exponential decay constants

• Thinnings= 5 years;• Softwood products: 59 years• Hardwood products: 92 years

• New IPCC method will subdivide wood products pool by end product category, e.g. wood panels

FORESTRY UNCERTAINTIES

• 5A Forest Land – uncertainty of 22% • Main sources of uncertainty:

• Afforestation model parameters• Afforestation input data• Forest soil carbon model choice• Afforestation model choice

• Afforestation model choice and parameters: move to the Forestry Commission CARBINE model for better representation of UK forest management

• Afforestation input data : these come from operational systems- have no associated statistical uncertainty- NFI will provide checks on reliability in future

• Forest soil carbon model choice- work is planned on this for 2013-14• Time consistency is good for forest activity data

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Carbon stock changes in vegetation and soils and greenhouse gas emissions from land use change

Calculating emissions: Land Use Change

LAND USE CHANGE ACTIVITIES PRODUCING GHG EMISSIONS

Sector category Details

Carbon stock change due to land use change

Uses land use change matrices and soil carbon and biomass modelling, with UK-specific activity data and model parameters

N2O emissions from disturbance

Uses forest and grassland land use change to cropland and IPCC default emission factors

Biomass burning (controlled and wildfires)

Controlled burning after forest land conversion: uses country-specific activity data and biomass densities, and IPCC default emission ratiosWildfires: new data for 1990-2011 inventory

LAND USE CHANGE

• Land use change affects:– Biomass (short term)– Soil carbon (long term

changes)

• Need to know land use changes between different land use types

• Current approach based on Countryside Survey data

0 10 20 30 40 50 60

Forest

Cropland

Grassland

Developed

Areas in 2000

0 10 20 30 40 50 60

Forest

Cropland

Grassland

Developed

Land use change 1990-2000

0 10 20 30 40 50 60

Forest

Cropland

Grassland

Developed

Areas in 1990

THE UK COUNTRYSIDE SURVEY SAMPLE SQUARES

LAND USE CHANGE ACTIVITY DATA 2• Countryside Survey data is not used for estimates of forest area

• Different definition of forest cover: 25% canopy cover at survey date vs. Forestry Commission 20% cover or potential to achieve it

• Inconsistent definitions between surveys• Forestry Commission statistics give complete coverage of new planting

• Land use change to Forest is calculated by the C-Flow model• Activity data for land use change from forest is compiled from other data

sources• LUC matrix/soil carbon model calculations are modified to take account of

these differences• Limitations of Countryside Survey dataset:

• Inflexible• Relatively small sample (879 squares for UK in 2007)• Discrepancy between land cover and land use• Multiple land use change over short time scales, e.g. through crop/grass rotations

are not captured well

LAND USE CHANGE SOIL CARBON MODEL

• UK has extensive data on soil type and soil property -> soil carbon density database

• Rates of change of soil carbon as a result of land use change are assumed to depend upon location and type of land use transition

• Method follows the IPCC GPG LULUCF but takes account of long term soil carbon dynamics

• Soil carbon changes due to LUC continue to be reported for many decades

FOREST CONVERSION TO OTHER LAND USE: DEFORESTATION• Affects carbon stock changes, N2O emissions from forest land

converted to cropland and controlled biomass burning• Area of forest conversion used to adjust areas Forest Land• 60% of biomass converted to HWP- reported as Loss in above-

ground biomass, and 40% is burnt on-site• Carbon stock changes in soils- calculated by the land use

change/soil carbon model• HWP is calculated using look-up tables from C-Flow model • Biomass burning uses default methodology and GHG emission

ratios

DEFORESTATION ACTIVITY DATA

Source data for • Forest-grassland conversion

• Unconditional felling licences from Forestry Commission

• England: 2000-2010• Scotland: 1999-2010• Wales: 1996-2010

• Use relative rates of woodland conversion from Countryside Survey 1990-1998 and 1999-2007 to gap-fill for:• 1990s• Conversion to Settlement

(Scotland and Wales)

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Carbon stock changes in vegetation and soils and greenhouse gas emissions from land management

Calculating emissions: Land Management

LAND MANAGEMENT ACTIVITIES PRODUCING GHG EMISSIONS

Sector category Details

Carbon stock change in Cropland

Carbon stock changes in biomass and soils due to yield improvements and lowland drainage, using country-specific activity data and emission factorsWork planned for this area

CO2 from liming on cropland and grassland

Uses agricultural lime sales volume and country-specific EFs

Carbon stock change in Grassland

Work planned for this area

Carbon stock change due to peat extraction activities

Uses country-specific activity data and a mixture of IPCC default and country-specific emission factors

Non-CO2 emissions due to peat extraction

Uses country-specific activity data and IPCC default emission factors

PEAT EXTRACTION• Uses extraction site

locations (from published Directory of Mines and Quarries) and Google Earth to measure areas of active extraction

• Sites categorised by production of peat for horticultural use (nutrient-poor) or fuel use (nutrient-rich)

• Horticultural peat extractor sales published annually

• Annual production and emissions are highly variable because extraction is weather dependent

UNCERTAINTIES FOR LAND MANAGEMENT AND LAND USE CHANGE• Uncertainty analysis undertaken 2011-2012• Looked at uncertainty in : input data, parameters,

structural/model choice• Monte Carlo simulations run to propagate input and parameter

uncertainty• Used standard deviation in output distributions as measure of

uncertainty

Afforestation Model Choice

Forest Soil C Model Choice

Peatland Drainage Parameters

LUC soil C Parameters

Afforestation Inputs

LUC soil C Model Choice

Afforestation Parameters

LUC soil C Inputs

250200150100500StDev (Gg C y-1)

• Areas undergoing land use change are the biggest uncertainty

UNCERTAINTIES FOR LAND MANAGEMENT AND LAND USE CHANGE

• Recommendations for reducing uncertainty from areas of land use change:– Other sources of land use data should be incorporated into

the inventory, so as to constrain the largest source of uncertainty.

– Move to a vector-based representation of land use data– Use a numerical optimisation procedure to reconcile

differences between data sets.• Good time series consistency for all key datasets

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Inventory development is driven by the need to reduce key uncertainties

Related research and development

PLANNED IMPROVEMENTS

• Improvements in 1990-2011 inventory• New data on wildfires (forests and moorland)• N2O emissions from drainage in forests

• Improvements to forestry data and modelling• Revision of Forest Land area when National Forest Inventory data is

finalised (awaiting statistics on woodland loss)• Assessment of carbon stock changes in pre-1921 woodland• Improvements to modelling of soils and roots• Replacement of C-Flow carbon accounting model with FC CARBINE

model

• Data assimilation to improve land use change matrices/vectors

• New research on the impact of cropland and grassland management on soil carbon

NEW RESEARCH PROJECT

IMPACT OF CROPLAND AND GRASSLAND MANAGEMENT ON SOIL CARBON (DEFRA SP1113)

• The first robust UK assessment• 2012-14 (7 partner organisations)• Key questions:

– Which management practices gain or lose the most soil carbon?

– How does this vary across the UK in space/time?

– What is the potential of land management to reduce GHG emissions now and in the future?

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Thank you for listening.

Questions?