Climate Change and Future Fire Regimes: Examples from California

Abstract

Climate and weather have long been noted as playing key roles in wildfire activity, and global warming is expected to exacerbate fire impacts on natural and urban ecosystems. Predicting future fire regimes requires an understanding of how temperature and precipitation interact to control fire activity. Inevitably this requires historical analyses that relate annual burning to climate variation. Fuel structure plays a critical role in determining which climatic parameters are most influential on fire activity, and here, by focusing on the diversity of ecosystems in California, we illustrate some principles that need to be recognized in predicting future fire regimes. Spatial scale of analysis is important in that large heterogeneous landscapes may not fully capture accurate relationships between climate and fires. Within climatically homogeneous subregions, montane forested landscapes show strong relationships between annual fluctuations in temperature and precipitation with area burned; however, this is strongly seasonal dependent; e.g., winter temperatures have very little or no effect but spring and summer temperatures are critical. Climate models that predict future seasonal temperature changes are needed to improve fire regime projections. Climate does not appear to be a major determinant of fire activity on all landscapes. Lower elevations and lower latitudes show little or no increase in fire activity with hotter and drier conditions. On these landscapes climate is not usually limiting to fires but these vegetation types are ignition-limited. Moreover, because they are closely juxtaposed with human habitations, fire regimes are more strongly controlled by other direct anthropogenic impacts. Predicting future fire regimes is not rocket science; it is far more complicated than that. Climate change is not relevant to some landscapes, but where climate is relevant, the relationship will change due to direct climate effects on vegetation trajectories, as well as by feedback processes of fire effects on vegetation distribution, plus policy changes in how we manage ecosystems.

Introduction to the Special Issue on Climate Change and Geosciences

“…Climate is not the sole controlling factor and vegetation response is an important consideration in fuel-limited environments. Human impacts can also affect the landscape propensity for burning through altering vegetation distribution and trajectories [20].…”

Changing Fire Regimes in Tropical and Subtropical Australia

“…Models that predict future fire regimes depend on relationships between annual temperature and fire activity that are based on historical studies correlating annual climate variation with fire activity, and at different spatial scales (Keeley and Syphard 2016). However according to Keane et al (2004) a major difficulty in predicting large-scale ecological change is the inclusion of non-equilibrium dynamics, disturbance regimes and spatial relationships into fire simulation models.…”

“…According to Keeley and Syphard (2016) as the climate changes, vegetation change is likely to occur independently and as a result of fire-climate relationships. This is further compounded by the spread of invasive vegetation that has the potential to increase fuel loads, change fire frequency and increase fire intensity resulting in a pyrogenic shift in vegetation (Brooks et al 2004).…”

“…These recent increases in large fires globally have caused concern about the influence that climate change and humans may have on future fire regimes (Pechony and Shindell 2010). According to Keeley and Syphard (2016), fire response to climatic variation is shown to be correlated to global circulation patterns such as the Pacific Decadal…”

“…Any prediction of future fire regimes requires an understanding of how temperature and precipitation interact in controlling fire activity (Keeley and Syphard 2016). Boer et al (2016), states that most studies on the impacts of climate change on fire regimes do not take into account transformational changes that take place in the relationship between climate, fire and vegetation.…”