GLEAM model in brief
GLEAM is a modelling framework that simulates the interaction of activities and processes involved in livestock production and the environment. The model is developed to assess livestock's impacts, adaptation and mitigation options at (sub)national, regional and global scale.
GLEAM differentiates key stages along livestock supply chains such as feed production, processing and transport; herd dynamics, animal feeding and manure management; and animal products processing and transport. The model captures the specific impacts of each stage, offering a comprehensive and disaggregated picture of livestock production negative side effects and a valuable information for intervention.
GLEAM is designed to analyze multiple environmental impact categories, such as greenhouse gas emissions, land use and land degradation, nutrient and water use and interaction with biodiversity. The main features of the current version of GLEAM are:
- Systematic, global coverage of six livestock species and their edible products: meat and milk from cattle, buffalo, sheep and goats; meat from pigs and meat and eggs from chicken.
- Spatially explicit modelling of livestock distribution, climatic data and feed yields that allows the capture of local production drivers and/or constraints, environmental impacts and identification of intervention measures.
- Estimation of greenhouse gas emissions from each stage of production. The model covers emissions of methane (CH4), carbon dioxide (CO2) and nitrous oxide (N2O).
- Use of Tier 2 methodology in animal derived emissions from enteric fermentation and manure management that provides more accurate information on how animal feeding and manure management options can help in mitigation.
A complete simulation of GLEAM produces multiple outputs which can be either final indicators and maps or intermediate calculations for subsequent operations. In its current version, GLEAM 1.0 outputs include:
- livestock animal numbers and their spatial distribution;
- production of manure and its management;
- animal feed rations composition and quality;
- livestock commodities production;
- emissions arising from each stage of production.
GLEAM is intended to assess the global impact of the livestock sector. Many of those impact, however, occur and are driven by (sub)-national or local environmental and social conditions. Thus, global averages and indicators are usually misleading and do not adequately help the understanding of real problems and how to tackle them.
To capture this variability, GLEAM uses regional or (sub)-national information on production practices and animal parameters. Additional data on livestock numbers, pasture and feed availability is incorporated with a resolution not coarser than 5 arc minutes (circa 10 x 10km at the equator). GLEAM produces the outputs at a spatial resolution of 3 arc minutes (circa 5 x 5km at the equator).