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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.

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.

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:

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:

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:

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:

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:

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:

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:

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.

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