Pyrogeography
Wildland fire occurs under certain conditions of climate, vegetation, topography, and sources of ignition, such that it has its own biogeography, or pattern in space and time.
Under the framework used in pyrogeography, there are three basic categories that control fire regimes across the world: consumable resources, ignitions and atmospheric conditions.
Due to the spatial and temporal characteristics of each variable, global fire behavior is a complex and fluid system to model and cannot be predicted by climate or vegetation alone.
Human influences can involve grazing, logging, suppression tactics, fuel treatments (preventative measures), and land use change such as deforestation and agricultural development.
Human influences include anthropogenic climate change and land management activity (logging, grazing, burning).
Since the late 1970s when satellite data became widely-available, the seasonal and geographical patterns of fire activity have come under inquiry, leading to the development of the field.
[citation needed] Spatial distribution models are used in pyrogeography to describe empirical relationships between fire and environmental factors.
Most models consist of mapped fire observations compared against various independent variables (in this case, spatial environmental gradients such as topography or precipitation).
Some of the variables used include things like net primary productivity (NPP), annual precipitation, temperature or soil moisture.
For example, deserts have very low NPP given the arid climate, and do not build up sufficient fuel loads to sustain fire.
[citation needed] On the other hand, areas with very high net primary productivity are generally constrained by wet tropical weather patterns.
This is seen in places such as tropical rainforests, where primary productivity is extremely high but the necessary weather conditions to dry out fuels do not exist.
It is in areas with intermediate levels of net primary productivity and climates with a seasonal pattern of sustaining fuel loads where fires regularly occur.
Tropical savannas are a clear example of these conditions, where hot, wet growing seasons are followed by dry periods that desiccate fuels and provide ignitions for fire.
This has been clearly demonstrated in the Amazon Basin and Indonesia, where massive deforestation and changing land use has altered the vast rainforest landscape and made it vulnerable to fire.
The expansion of suburbs and neighborhoods into regions that tend to burn frequently or intensely (such as parts of California) means that homeowners face increasing risks of wildfires spreading or starting in their area.
Knowledge of past fire regimes comes from geochemistry, tree ring analysis, charcoal, written documents and archeology.
This relationship between fire and vegetation present is used to make inferences about the climate at that time, based on the amount and kinds of charcoal found.
