De definitie van droogte is aan een update toe. Het is tijd om te erkennen dat naast variaties in klimaat ook menselijk handelen droogte veroorzaakt of beïnvloedt. Wereldwijde samenwerking tussen natuur- en sociaalwetenschappers is daarom hard nodig, stelt een groep internationale onderzoekers, waaronder drie van Wageningen University, in een commentaar in Nature GeoScience van februari.
Drought is a phenomenon that is not only caused by nature and climate, and the use of water is not an exclusively social-economic occurrence. People influence drought and respond to it. They build irrigation dams, drill or re-drill deeper for groundwater, adapt their land use, save water or ignore an extraction ban. The recent heavy drought in Brazil, for instance, cannot be explained as exclusively a natural disaster. Deforestation, urbanisation and the construction of water reservoirs also play a role.
Impact of drought
The impact of human actions on drought, however, is difficult to put into real terms. This makes it hard to determine whether water management organisations should respond to drought caused by climate variations or tackle the human actions that played a part in causing the drought. In addition, the impact of drought on the income of farmers cannot be viewed as isolated from the impact of policy on access to water, water use, water pollution and political instability.
Three types of drought
For this reason, in an article published in Nature, a group of eighteen collaborating specialists consisting of hydrologists, climatologists, social geographers, and water and environmental management specialists, call for the recognition of three types of drought: caused by climate, caused by humans, and influenced by humans. In this area, they have identified knowledge gaps in various areas. ‘We still know too little about the influence of humans on the impact of precipitation shortages on lower groundwater reserves and rivers, about the influence of changes in land use on drought or about how the various causes - climate and people - contribute to drought,’ says one of the researchers, Henny van Lanen of Wageningen University. ‘We also need to gain a better understanding of people’s perception of drought and their adaptation mechanisms and build datasets on human actions and the impact of these actions on drought.’
‘If the natural and social sciences join forces much more is possible,’ van Lanen explains. ‘Take for instance the river basin of the Júcar River in Spain. This was fully caused by humans. But because a united effort was made and a plan was developed that took into account the hydrology, water extraction and stakeholders, during periods of drought the water is still sufficient for the various functions.’ In other words, a multidisciplinary approach is needed. What are the consequences if nothing changes? ‘Periods of drought will become more intense everywhere, but in Europe, Southern Europe will be most affected. The question is how people will respond to this. Perhaps they will resort to using more groundwater. The danger of overuse of groundwater, however, is that you cannot see when reserves are depleting, so there is no sense of urgency like there is when a lake dries up.’
The basis for the article in Nature is Wageningen UR’s drought research within the context of the Sixth and Seventh EU Framework Programme (FP6, FP7), to which the WUR authors Henny van Lanen, Ryan Teuling and Remko Uijlenhoet also contributed. Many researchers became acquainted through the network of the European Drought Centre (EDC), managed by Wageningen University and the University of Oslo.