Demeter

A land-use and land-cover disaggregation and change detection model

Demeter is an open source Python package that was built to disaggregate projections of future land allocations generated by an integrated human-Earth systems model. Projected land allocation from these models are traditionally transferred to Earth System Models (ESMs) in a variety of gridded formats and spatial resolutions as inputs for simulating biophysical and biogeochemical fluxes. Existing tools for performing this translation generally require a number of manual steps which introduces error and are inefficient. Demeter makes this process seamless and repeatable by providing gridded land use and land cover change (LULCC) products downscaled directly from the Global Change Analysis Model (GCAM) in a variety of formats and resolutions commonly used by ESMs.

Getting Started with Demeter

Set up Demeter using the following steps:

1. Install Demeter from GitHub:

   pip install git+http://github.com/JGCRI/demeter.git#egg=demeter

2. Download the example data using the following in a Python prompt:

   import demeter
   
   # the directory that you want to download and extract the example data to
   data_dir = "<my data download location>"
   
   # download and unzip the package data to your local machine
   demeter.get_package_data(data_dir)

3. Setup your configuration file (.ini). Examples are located in the "example" directory that you just downloaded. Be sure to change the following variables to represent the local path. See the details for custom runs in the Setup section of this file.

4. To run Demeter:

   import demeter
   
   # the path and file name that my example configuration (.ini) file was downloaded to
   config_file = '<path to my example config file>/demeter_config.ini'
   
   # run all time steps
   demeter.run_model(config_file=config_file,
                     write_outputs=True)

Setup

Demeter requires the setup of several input files to begin a run. Examples of all input files can be found in the ‘examples’ directory and the expected file structure is outlined in the following:

• Example directory
  • Inputs directory
    • Allocation directory
      • Constraint weighting file
        • GCAM landclass allocation file
        • Kernel density weighting file
        • Spatial landclass allocation file
        • Transition priority file
        • Treatment order file
    • Observed spatial data directory
      • Observed spatial data file
    • Constraint data directory
      • Constraint files
    • Projected GCAM land allocation directory
      • GCAM land allocation file

The following describes the requirements and format of each input.

Observed spatial data:

This file represents the area in square degrees of each land class existing within a grid cell. The grid cell size is defined by the user. This file must be presented as a comma-separated values (CSV) file having a header in the first row and must contain the field names and fields described in Table 1.

Field	Description
fid	Unique integer ID for each grid cell latitude, longitude
landclass	Each land class field name (e.g., shrub, grass, etc.). Field names must not include commas.
region_id	The integer ID of the GCAM region that the grid cell is contained in. Exact field name spelling required.
metric_id	The integer ID of the GCAM basin that the grid cell is contained in. Exact field name spelling required.
latitude	The geographic latitude value of the grid cell centroid as a signed float. Exact field name spelling required.
longitude	The geographic longitude value of the grid cell centroid as a signed float. Exact field name spelling required.

Table 1. Observed spatial data required fields and their descriptions.

Projected land allocation data:

This file is the formatted GCAM run output for land allocation projections. Since the format of this file can vary based on GCAM user preference, the file must be formatted to meet Demeter input requirements as described in Table 2. The file must be a CSV file having the header in the first row.

Field	Description
region	The text name of the GCAM region. Exact field name spelling required.
landclass	Each land class field name (e.g., shrub, grass, etc.). Field names must not include commas.
year	Each year of the GCAM run as an integer (e.g., 2005, 2010, etc.)
metric_id	The integer ID of the GCAM basin. Exact field name spelling required.

Table 2. Projected land allocation required fields from GCAM.

Allocation files:

Projected land class allocation:

This file defines how the land-use and land-cover classes in the GCAM projected land allocation data will be binned into final classes. See the projected land class allocation file in the example inputs for reference.

For example:

category	demeter_class_1	demeter_class_2	demeter_class_3
gcam_class_1	0	0	1
gcam_class_2	0	0	1
gcam_class_3	0	1	0
gcam_class_4	0	1	0
gcam_class_5	1	0	0

Observational spatial data class allocation:

This file defines how the land-use and land-cover classes in the OSD will be binned into final land classes for output, which can be defined by the user and serve to place projected land allocation data from GCAM on a common scale with the on-the-ground representation of land-use and land-cover represented in the OSD. See the Observed spatial data class allocation file in the example inputs for reference.

For example:

category	demeter_class_1	demeter_class_2	demeter_class_3
observed_class_1	1	0	0
observed_class_2	1	0	0
observed_class_3	0	1	0
observed_class_4	0	1	0
observed_class_5	0	0	1

Constraint weighting:

Constraints such as soil quality may be desirable to the user and can be prepared by assigning a weighted value from 0.0 to 1.0 for each grid cell in the OSD. Spatial maps of constraints should be provided by the user for application during the downscaling process. Users should note that constraining a grid cell to 0.0 may impede the ability to be able to achieve a projected land allocation from GCAM since land area is being excluded that GCAM expects. Each constraint file must have two fields: fid and weight. The fid field should correspond to the fid field in the OSD input and the weight field should be the weight of the constraint per the cell corresponding to the OSD input. Each file should be a CSV with no header.

For example:

category	demeter_class_1	demeter_class_2	demeter_class_3
nutrient_availability	0.0	0.4	0.0
soil_quality	0.0	0.2	0.0

Kernel density weighting:

Weight the degree to which land classes subjected to a kernel density filter will be utilized during expansion to each class. Value from 0.0 to 1.0. See the kernel density weighting file in the example inputs for reference.

For example:

category	demeter_class_1	demeter_class_2	demeter_class_3
kernel_density	1.0	0.4	1.0

Transition Priority:

This ordering defines the preferential order of final land allocation (e.g., crops expanding into grasslands rather than forests). See the priority allocation file in the example inputs for reference. See the priority allocation file in the example inputs for reference.

For example:

category	demeter_class_1	demeter_class_2	demeter_class_3
demeter_class_1	0	1	2
demeter_class_2	1	0	2
demeter_class_3	1	2	0

Treatment order:

Defines the order in which final land classes are downscaled. This will influence the results (e.g., if crops are downscaled first and overtake grassland, grassland will not be available for shrubs to overtake when processing shrub land). See the treatment order file in the example inputs for reference.

For example:

category	order
demeter_class_1	3
demeter_class_2	2
demeter_class_3	1

Constraints (not required):

A weight for each constraint, with a value ranging from -1.0 to 1.0, can be applied to each land class. If no constraints are desired, a user should simply provide a header-only file. For example, for a given land class, the weight for the soil quality constraint with a value of -1 indicates that one land class is fully constrained inversely (e.g., grasslands are opportunistic and grow readily in areas with a low soil quality); a weight of 0 indicates that soil quality exerts no constraint to the land class (e.g., forest, etc.); a weight of 1 for soil quality indicates that high soil quality will highly influence where the type will be spatially allocated (e.g. cropland). These constraints are developed in separate files as described in the following Constraints section. See the constraint weighting file in the example inputs for reference.

For example:

target_fid	value
1	0.5
2	0.7
3	0.9
4	0.0
5	0.1

Configuration file:

Demeter’s configuration file allows the user to customize each run and define where file inputs are and outputs will be. The configuration options and hierarchical level are described in Table 3.

Level	Parameter	Description
STRUCTURE	run_dir	The full path of the root directory where the inputs and outputs directory are stored
STRUCTURE	input_dir	The name of the input directory
STRUCTURE	output_dir	The name of the output directory
INPUTS	allocation_dir	The name of the directory that holds the allocation files
INPUTS	observed_dir	The name of the directory that holds the observed spatial data file
INPUTS	constraints_dir	The name of the directory that holds the constraints files
INPUTS	projected_dir	The name of the directory that holds the GCAM projected land allocation file
INPUTS - ALLOCATION	spatial_allocation_file	The file name with extension of the observed spatial data class allocation
INPUTS - ALLOCATION	gcam_allocation_file	The file name with extension of the projected land class allocation
INPUTS - ALLOCATION	kernel_allocation_file	The file name with extension of the kernel density weighting
INPUTS - ALLOCATION	transition_order_file	The file name with extension of the priority allocation
INPUTS - ALLOCATION	treatment_order_file	The file name with extension of the treatment order
INPUTS - ALLOCATION	constraints_file	The file name with extension of the constraint weighting
INPUTS - OBSERVED	observed_lu_data	The file name with extension of the observational spatial data
INPUTS - PROJECTED	projected_lu_data	The file name with extension of the projected land allocation data from GCAM
OUTPUTS	diagnostics_output_dir	The name of the directory that diagnostics outputs will be kept
OUTPUTS	log_output_dir	The name of the directory that the log file outputs will be kept
PARAMS	scenario	Scenario name
PARAMS	run_desc	The description of the current run
PARAMS	observed_id_field	Observed spatial data unique field name (e.g. target_fid)
PARAMS	start_year	First time step to process (e.g., 2005)
PARAMS	end_year	Last time step to process (e.g., 2100)
PARAMS	use_constraints	1 to use constraints, 0 to ignore constraints
PARAMS	spatial_resolution	Spatial resolution of the observed spatial data in decimal degrees (e.g. 0.25)
PARAMS	errortol	Allowable error tolerance in square kilometres for non-accomplished change
PARAMS	timestep	Time step interval (e.g., 5 years) for the output data. This time step is the increment that Demeter will process when starting with the base year.
PARAMS	proj_factor	Factor to multiply the projected land allocation by
PARAMS	diagnostic	0 to not output diagnostics, 1 to output
PARAMS	intensification_ratio	Ideal fraction of land change that will occur during intensification. The remainder will be through expansion. Value from 0.0 to 1.0.
PARAMS	stochastic_expansion	0 to not conduct stochastic expansion of grid cells, 1 to conduct
PARAMS	selection_threshold	Threshold above which grid cells are selected to receive expansion for a target functional type from the kernel density filter. Value from 0.0 to 1.0; where 0 lets all land cells receive expansion and 1 only lets only the grid cells with the maximum likelihood expand.
PARAMS	kernel_distance	Radius in grid cells used to build the kernel density convolution filter used during expansion
PARAMS	target_years_output	Years to save data for; default is ‘all’; otherwise a semicolon delimited string (e.g., 2005; 2020)
PARAMS	save_tabular	Save tabular spatial land cover as a CSV; define tabular units in tabular_units param
PARAMS	tabular_units	Units to output the spatial land cover data in; either ‘sqkm’ or 'fraction'
PARAMS	save_transitions	0 to not write CSV files for each land transitions per land type, 1 to write
PARAMS	save_netcdf_yr	0 to not write a NetCDF file for each year of the fraction of land cover of each land class by grid cell; 1 to write

Table 3. Configuration file hierarchy, parameters, and descriptions.