On the other hand, it helps the recovery process, as assistance flows in from regions outside the disaster area. By many measures, the world s environment has become severely degraded during this century. This trend is expected to continue. Environmental degradation has been cited as one of the factors contributing to some disasters. For example, extensive logging increasing runoff contributed to flooding problems in China.
Urbanization can be important as well, particularly with respect to urban floods.
The paving over of natural surfaces increases runoff during extreme rainfall events, by reducing the infiltration of water into the ground. Many parts of Ontario, particularly in the greater Toronto region have seen extensive urbanization over the past few decades. With many sewer systems designed for relatively short return period rainfalls, the potential for disastrous flooding has increased. Climate change seems likely to increase disasters globally, through rising sea levels, by increasing the intensity of the hydrological cycle and the frequency of heat waves and droughts. Possibly an enormous catastrophe could result at some time, if the climate rapidly switched into a new state, by shutting off the deep-ocean Conveyor Belt in the Atlantic, for example.