5.4C - Drought and Ecosystems
The impacts of drought on ecosystem functioning (wetlands, forest stress) and the resilience of these ecosystems.
Ecological resilience is the capacity of an ecosystem to withstand and recover from a natural event (e.g. drought or flooding) or some form of human disturbance.
Wetlands
Wetlands currently cover about 10% of the Earth's land surface and until 50 years ago they were considered as wastelands, only good for draining and infilling to provide building land. However, it is now understood that wetlands perform a number of important functions: from acting as temporary water stores to the recharging of aquifers, from giant filters trapping pollutants to providing nurseries for fish and feeding sites for migrating birds.
Drought can have a major impact on wetlands. With less precipitation there will be less interception (as vegetation becomes stressed), as well as less infiltration and percolation. Water tables will fall. Evaporation will also increase. This, together with the decrease in transpiration, will reduce the valuable functions performed by wetlands.
While droughts pose a threat to wetlands, the major challenge to their survival still remains artificial damage.
Resilience???
Drought can have a major impact on wetlands. With less precipitation there will be less interception (as vegetation becomes stressed), as well as less infiltration and percolation. Water tables will fall. Evaporation will also increase. This, together with the decrease in transpiration, will reduce the valuable functions performed by wetlands.
While droughts pose a threat to wetlands, the major challenge to their survival still remains artificial damage.
Resilience???
Forests
Forests have significant impacts on the hydrological cycle. They are responsible for much interception which, in turn, means reduced infiltration and overland flow. Forests are characterised by high levels of transpiration.
Like wetlands, drought threatens forests, but it is people and deforestation that most threaten their survival. In coniferous forests, drought is not only causing direct physiological damage but it is also increasing the susceptibility of pines and firs to fungal diseases. Tree mortality is on the increase. The same applies to the tropical rainforest, expect that the increased mortality attributed to drought appears to be having a greater impact on large trees. Here there is the added concern of what this increased tree mortality will eventually do to this incredibly important carbon store.
As ecosystem play such a vital role within the hydrological cycle, it is important to ensure that their ecological resilience is not overstretched by either the destructive activities of people or natural events such as droughts and floods.
Resilience?
Like wetlands, drought threatens forests, but it is people and deforestation that most threaten their survival. In coniferous forests, drought is not only causing direct physiological damage but it is also increasing the susceptibility of pines and firs to fungal diseases. Tree mortality is on the increase. The same applies to the tropical rainforest, expect that the increased mortality attributed to drought appears to be having a greater impact on large trees. Here there is the added concern of what this increased tree mortality will eventually do to this incredibly important carbon store.
As ecosystem play such a vital role within the hydrological cycle, it is important to ensure that their ecological resilience is not overstretched by either the destructive activities of people or natural events such as droughts and floods.
Resilience?