About
GAEZ+_2015 Monthly metadata
Steve Frolking1, Stanley Glidden1, Danielle Grogan1, Alexander Proussevitch1, Dominik Wisser2
1 Institute for the Study of Earth Oceans and Space, University of New Hampshire, USA
2 Food and Agriculture Organization of the United Nations
Contact information:
Steve Frolking, steve.frolking@unh.edu
Danielle Grogan, Danielle.Grogan@unh.edu
Dominik Wisser, Dominik.Wisser@fao.org
1. INTRODUCTION
This dataset, GAEZ+_2015 Monthly, provides global gridded (5-arcminute resolution) irrigated and rainfed cropland areas for 26 different crops/crop categories by month (see Table 1 for crop list below). This new product is derived from the GAEZ+_2015 Annual data product (Frolking et al., 2020).
2. METHODOLOGY
Two datasets were used to produce monthly cropland area by crop and by irrigated vs rainfed management. These are:
- GAEZ+ 2015 Annual Harvested Area (Frolking et al., 2020)
- MIRCA2000 cropland area (Portmann et al., 2008)
Table 1. List of GAEZ crop categories used in all GAEZ+ 2015 products, as well as the matching between GAEZ+ 2015 crops and MIRCA2000 crop categories for the purposes of producing GAEZ+ 2015 monthly cropland data. The Priority for Removal column lists the order in which cropland (rainfed first, the irrigated) are removed from a grid cell in the case that the monthly cropland area exceeds the grid cell area.
|
GAEZ crop |
MIRCA2000 crop |
1:1 Matching |
Priority for removal |
|
Banana |
Others perennial |
No |
3 |
|
Barley |
Barley |
YES |
18 |
|
Cassava |
Cassava |
YES |
11 |
|
Cotton |
Cotton |
YES |
4 |
|
Crops NES |
Others perennial AND others annual |
No |
2 |
|
Foddercrops |
Fodder grasses |
no |
2 |
|
Groundnut |
Groundnut |
YES |
6 |
|
Maize |
Maize |
YES |
20 |
|
Millet |
Millet |
YES |
16 |
|
Oil palm fruit |
Oil palm |
YES |
8 |
|
Olives |
Others perennial |
No |
3 |
|
Other cereals |
Rye AND Millet |
No |
17 |
|
Potato & Sweet potato |
Potatoes |
YES |
12 |
|
Pulses |
Pulses |
YES |
5 |
|
Rapeseed |
Canola |
YES |
7 |
|
Rice |
Rice |
YES |
19 |
|
Sorghum |
Sorghum |
YES |
15 |
|
Soybean |
Soybeans |
YES |
14 |
|
Stimulants |
Others annual |
No |
1 |
|
Sugarbeet |
Sugarbeet |
YES |
9 |
|
Sugarcane |
Sugarcane |
YES |
10 |
|
Sunflower |
Sunflower |
YES |
13 |
|
Tobacco |
Others annual |
No |
1 |
|
Vegetables |
Others annual |
No |
1 |
|
Wheat |
Wheat |
YES |
21 |
|
Yams & other roots |
Others annual |
No |
1 |
Harmonize the GAEZ+ 2015 and MIRCA2000 crop lists
The MIRCA2000 cropland product provides monthly growing area grids for 26 irrigated and rainfed crops and crop categories, as well as cropping calendars that identify the planting month and harvesting month for each crop (via ‘subcrops’ – see below). However, the MIRCA2000 crop list is not the same as the GAEZ+ 2015 crop list; we matched each crop type in the GAEZ+ 2015 crop list to a crop type in the MIRCA2000 crop list to enable the application of MIRCA2000 crop calendars to GAEZ+ 2015 crops (Table 1). Out of the 26 GAEZ+ 2015 crops, 18 had clear 1:1 matching crop categories within MIRCA2000. The remaining 8 crops were matched based on general crop characteristics, i.e., annual vs. perennial, or to unmatched MIRCA2000 cereals.
An essential component of the MIRCA2000 cropland dataset is the identification subcrop categories within each crop category to split crops into areas grown in different seasons. Up to 5 subcrops can be defined to represent such multicropping practices. Below, we use the following notation:
HG = annual harvested area from the GAEZ+ 2015 product for a given crop
HM = annual harvested area calculated from the MIRCA2000 data for a given crop
AM,n = cropland area of MIRCA2000 crop, subcrop n, by month
AG,n = cropland area of GAEZ+ 2015 crop, subcrop n, by month
AG = cropland area of GAEZ+ 2015 crop, by month
Apply MIRCA2000 monthly crop calendars to GAEZ+ 2015 annual data
To generate the monthly cropland area of GAEZ+ 2015 crops, we followed these steps for each GAEZ crop in each grid cell:
- For a given GAEZ crop in a given grid cell, is there >0 area reported for the matching MIRCA2000 crop?
- If YES, then use the MIRCA2000 data for the grid cell and crop considered
- If NO, then find the closest grid cell with the matching MIRCA200 crop category, and apply the MIRCA2000 crop rotation from that grid cell to the given crop/grid cell combination for the following steps.
- Does the matching MIRCA2000 crop category (Table 1) have more than 1 subcrop?
- If NO, then AG = HG for all months of the cropping season, as defined by the MIRCA2000 crop calendar.
- If YES, then for each subcrop category n, apply the ratio of AM,n/HM to HG, then sum the subcrop areas within each month such that:
AG = SUM(AM,n/HM) x HG
- For each month and each grid cell, check if the sum of all crops (irrigated and rainfed) is greater than the 99 % of area of the grid cell. We assume that at least 1 % of land must be retained as non-cropland for agricultural infrastructure such as roads, buildings, irrigation equipment, and other landcovers (e.g. rivers, wetlands).
- If NO, then no further processing is done.
- If YES, then reduce crop area by the excess value based on a priority order (Table 2) Rainfed crops have higher priority order for the excess truncation (starting with 1) before removing irrigated crops, until the cell area is not exceeded. A large priority number (e.g., 20) indicates a low priority, such that the crop’s land is unlikely to be removed. Large priority numbers are given to the staple crops to ensure these important food producing lands are consistent with FAOSTAT country data.
The maximum monthly amount of cropland that was removed by step 3 is 711,543 ha, which is 0.05% of total global cropland area.
3. RESULTING PRODUCTS
This new data product consists of 93 data files in netCDF format, one rainfed cropland area file and one irrigated cropland area file for each of the 26 GAEZ crop/subcrop categories. Each netCDF file contains 12 layers, one per month.
File format: netCDF v.4 with default internal compression (level 7)
File naming convention: GAEZ_CropArea_{Cropname}_{subcrop}_{Management}.nc
where: {Cropname} is one of the names from column 1 in Table 1.
{subcrop} is a number (1 through 5) indicating crop rotations.
{Management} is Irrigated or Rainfed.
Date Produced: January 2021.
GIS layer info:
Extent: X: -180 to +180
Extent Y: -90 to +90
Extent Z: 12, one layer per month
Resolution: 0.083333 decimal degrees (5 arcminutes)
Projection: CRS “+proj=longlat +datum=WGS84 +no_defs +ellps=WGS84 +towgs84=0,0,0”.
EPSG code is “EPSG:4326”. Other common projection name aliases: “WSG84”.
Units: Cropland Area: 1000 ha (107 m2) per 5-arcminute grid cell
No data value: Oceans, open-water, and Antarctica in the netCDF files have the no-data value of -3.4e+38.
4. REFERENCES
Frolking S., Wisser D., Grogan D., Proussevitch A., Glidden S. (2020) GAEZ+_2015 Crop Harvest Area, https://doi.org/10.7910/DVN/KAGRFI, Harvard Dataverse, V1.
Portmann F.T., Siebert F., and Doell P. 2008. MIRCA2000 – Global monthly irrigated and rainfed crop areas around the year 2000: A new high-resolution data set for agricultural and hydrological modelling. Global Biogeochemical Cycles, 24, GB1011, doi:10.1029/2008GB003435.
