Smoke from biomass fires makes up a substantial portion of global greenhouse gas, aerosol, and black carbon (GHG/A/BC) emissions. Understanding how fuel characteristics and conditions affect fire occurrence and extent, combustion dynamics, and fuel consumption is critical for making accurate, reliable estimates of emissions production at local, regional, national, and global scales. The type, amount, characteristics, and condition of wildland fuels affect combustion and emissions during wildland and prescribed fires. Description of fuel elements has focused on those needed for fire spread and fire danger prediction. Knowledge of physical and chemical properties for a limited number of plant species exists. Fuel beds with potential for high impact on smoldering emissions are not described well. An assortment of systems, methods, analytical techniques, and technologies have been used and are being developed to describe, classify, and map wildland fuels for a variety of applications. Older systems do not contain the necessary information to describe realistically the wildland fuel complex. While new tools provide needed detail, cost effectiveness to produce a reliable national fuels inventory has not been demonstrated. Climate change-related effects on vegetation growth and fuel distribution may affect the amount of GHG/A/BC emissions from wildland fires. A fundamental understanding of the relationships between fuel characteristics, fuel conditions, fire occurrence, combustion dynamics, and GHG/A/BC emissions is needed to aid strategy development to mitigate the expected effects of climate change. Published by Elsevier B.V.