Saturday, July 10, 2021

Meteorological or anthropogenic drought? A recent study illustrates the environmental, social and economic risks

by Silvia Peppoloni*

This article was published in ReWriters Magazine, in Italian and English:

* Istituto Nazionale di Geofisica e Vulcanologia, Rome (Italy); Secretary General of the IAPG - International Association for Promoting Geoethics; Councillor of the IUGS - International Union of Geological Sciences; Member of the Ethical Board of ICOS - Intergrated Carbon Observation System; Coordinator of IAPG-Italy; Member of the Board of Directors of the Italian Geological Society. Email:

Silvia Peppoloni
Included among the meteorological phenomena, drought is defined as the lack or scarcity of rain that lasts for an exceptionally long period of time (months to years), during which rainfall is scarce or insufficient to guarantee the balance between the natural availability of water and its consumption by the human being.

In many regions of the Earth, drought is a recurring phenomenon, even with a certain periodicity, and in this sense it can be faced with appropriate strategies and actions. These include marine desalination works, the collection and storage of rainwater, the planting of crops that need low quantities of water, or recycling with purification of water already used.

Drought can cause a serious risk for the territory and the people who live there, as it involves severe environmental (fires, desertification), economic (reduction of cultivated areas, losses in industrial, agricultural and livestock activities) and social (famine, migration) mass, social tensions, wars) consequences. For this reason it should not be considered only an effect of the water deficit, but it should be studied, modeled and parameterized including also the anthropic interactions with nature. It is on this point that the authors of a recent article published in the scientific journal Reviews of Geophysics insist: there is also the “anthropogenic drought”, where it is human activities rather than natural factors that cause or intensify drought and its impact.

But how is it possible to incorporate anthropogenic drought into forecasting models, so that its effects can be planned and mitigated for the future?

Drought: a multidimensional phenomenon

The intensity of the drought is expressed through indices: the most used internationally is the Standardized Precipitation Index (SPI), whose value quantifies the surplus or deficit of rainfall compared to the average values. However, this indicator explains the availability of water from a meteorological point of view, but does not consider the bidirectional interactions between human action and the environment, especially it does not take into account the way in which human activities can change rainfall, increase the risk of water stress or altering the microclimatic conditions. It also does not consider the impact of local water demand or land management practices. For this reason the authors believe it is more effective to define and treat drought as a multidimensional and multiscale phenomenon.

The evidence of this methodological perspective is immediate, if we consider the combined effects of climate change and human activities. Multivariate climatic conditions could make the negative impacts of drought events more devastating, as the planet’s temperatures will continue to rise in the coming years, with unpredictable repercussions on water demand and water use, particularly with increases in demand by the agricultural sector. Furthermore, the frequency and distribution of droughts can affect renewable energy production and current and future economic balances which, in turn, can increase the anthropogenic CO2 footprint and subsequently affect rainfall conditions and the severity of the anthropogenic drought, in a negative feedback mechanism. In addition, drought can change the length of the plant growing season, local hydrology and the carbon uptake period.

Making forecasts on drought is in general very difficult, but predicting and planning interventions by introducing anthropogenic drought into the analysis models can be a real challenge for science, due to the different rates of development and the different demand for water that characterizes various countries and regions of the world.

However, despite the gloomy picture, we can be cautiously optimistic: the progress in the development of dynamics models of the water / human interaction system and the Integrated Assessment Models (IAM), that are able to dynamically represent the interactions between natural and anthropogenic components at different scales, for example by inserting climatic data in the analyzes to elaborate future scenarios, are proving effective. In fact, through the use of these models it seems possible to identify scenarios in line with future climate projections, which are very useful for making technical choices and political actions, and for evaluating their possible results in advance.

There are, however, some limitations: the models developed so far are more suitable for investigating large-scale events, which occur over a long period of time, but instead present greater uncertainty in predicting short-term and regional-scale effects (such as local droughts).

The real possibility remains that this new way of studying drought, by introducing the anthropogenic factors that influence it, can come to provide increasingly accurate predictive scenarios, able to guide the environmental and development policies of human communities.

Improving the response to future droughts through increasingly effective strategies for managing the demand and water supply of the future, when the climate will be warmer and characterized by numerous extreme climatic events, is not just an issue of economic sustainability. It is also and above all a great safety issue, which affects everyone, since the drought may be accompanied by growing social and geopolitical tensions. Only responsible and farsighted ruling classes and ever more accurate science and technology will be able to try to defuse the effects of the massive anthropogenic global changes taking place.


Other articles published in the IAPG Blog:

IAPG - International Association for Promoting Geoethics

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