Like most of southern California, the majority of San Diego's current area was originally occupied by chaparral, a plant community made up mostly of drought-resistant shrubs. The endangered Torrey pine has the bulk of its population in San Diego in a stretch of protected chaparral along the coast. The steep and varied topography and proximity to the ocean create a number of different habitats within the city limits, including tidal marsh and canyons. The chaparral and coastal sage scrub habitats in low elevations along the coast are prone to wildfire, and the rates of fire have increased in the 20th century, due primarily to fires starting near the borders of urban and wild areas.