| Popis: |
Human activities affect fire in many ways, often unintentionally or with considerable time-lags before they manifest themselves. Anticipating these changes is critical, so that insidious impacts on ecosystems, their biodiversity, and associated goods and services can be avoided, mitigated or managed. To aid this, we develop a conceptual framework based on the notion of an ignition catchment, or the spatial extent and temporal range where an ignition is likely to result in a site burning. Ignition catchments can be altered by any factor that changes the spatial pattern or temporal frequency of ignitions, or the size or temporal range of the catchment. This framework is highly flexible and allows detection or prediction of changes in the fire regime, the threat this poses for ecosystems or fire risk, and areas where management interventions and/or monitoring are required.We illustrate the approach by exploring the impact of anthropogenic land cover change on fire and biodiversity in adjacent ecosystems on the hyper-diverse Cape Peninsula, South Africa. We use fire models to estimate spatial changes in burn probability between historical and current land cover and predict the observed record of fires and forest encroachment into fire-dependent Fynbos ecosystems in Table Mountain National Park. Urban expansion has created anthropogenic fire shadows that are modifying fire return intervals, facilitating a state shift to low-diversity, non-flammable forest at the expense of hyperdiverse, flammable Fynbos ecosystems. Despite occurring in a conservation area, these ecosystems are undergoing a hidden collapse and desperately require intervention.Anthropogenic fire shadows can be caused by many human activities and are likely to be a universal phenomenon, contributing to the observed global decline in fire activity, but also causing extreme fires in ecosystems where there is no shift to a less flammable state and flammable fuels accumulate. Identifying anthropogenic impacts on ignition catchments is key for both understanding global impacts of humans on fire and guiding management of human-altered landscapes for desirable outcomes. |
