REPORT
Droughts will be more intense and frequent
Published on October 15th, 2015
Droughts could become more frequent and more severe in the Iberian Peninsula, thus representing one of the most serious consequences of global warming and climate change. With droughts, which go hand in hand with fires, vegetation and agriculture will suffer. The solution may lie in monitoring and the early detection of droughts and the timely implementation of adaptation measures.
"Most climate models point to a general increase in the frequency and severity of droughts worldwide and, in particular, on the Iberian Peninsula, which has been clearly affected by an intensification of dryness”, claims Célia Gouveia, a professor at the Faculty Sciences of the University of Lisbon and coordinator of the QSECA Project, funded by the Foundation for Science and Technology (FCT).
As part of the Mediterranean Basin, the Iberian Peninsula is considered one of the most sensitive areas to the impacts of climate change. These include the rise in temperature, and consequently of the frequency of heat waves, as well as the great variability of the average precipitation in depth pattern and of the water availability. All of these factors are associated with the increase in severe droughts. There are still many uncertainties, particularly with regard to precipitation in Portugal, as the head of QSECA emphasises.
Starting in 2013, the QSECA project aims to monitor, assess and characterise droughts recorded in the Iberian Peninsula in the past and present, through their relationship with the weather. The intention is to improve the understanding, diagnosis, and modulation of these extreme events and of their impact in the future. “We will only be able to predict what will happen in the future if we can understand what happened in the past, and what is currently happening”, she comments.
One of the objectives of QSECA is to develop information and diagnostic tools for droughts, notably through the implementation of a drought index recently developed by the research group of Vicente-Serrano (Spanish National Research Council – IPE-CSIC) integrating the project. The SPEI index - Standardized Precipitation Evapotranspiration Index- includes the effect of temperature by modelling evapotranspiration, a parameter that Célia Gouveia considered “very important” in a climate change context.
The group will also use satellite derived vegetation indices to assess the impact of drought on vegetation. The data will be disclosed not only to the scientific community but also to policy makers. “We plan to equip competent authorities with information and tools to make the right decisions”, mentions the coordinator.
Drought impacts yesterday, today and tomorrow
Droughts are not a new phenomenon. According to Célia Gouveia, data from the last 60 years indicate a “general trend of increased dryness in the Iberian Peninsula. This trend is more significant in some areas, due to the variability of precipitation and the increasing evaporative demand”.
Paleoclimatology studies developed by Spanish researchers based on lake sediments found a relationship between the existence of extreme drought in the past and the disappearance of civilisations. The results of these studies were presented recently at a workshop organised by the QSECA project in Lisbon.
While it is difficult to accurately predict all the effects of extreme events in Portugal, it is known that the drought has profound impacts on various systems, from agriculture to forests, including water resources and the national economy.
The coordinator of QSECA has studied, in particular, the effects of drought on vegetation. “In the Iberian Peninsula, there is a strong correlation between the most extreme events of drought and the activity of the vegetation”, she affirms.
Indeed, “the increase in the frequency and severity of droughts, together with heat waves, impacts the vegetation at various levels, including the variability of vegetation, the carbon balance, soil degradation, and agricultural productivity, especially cereals, which are dryland cultures that are highly dependent on rainfall. In some cases, recurring and intense droughts can even lead to the death of trees, similar to the events that occurred in some regions during the severe drought of 2012. The recovery could take years”.
As for the carbon balance, it is known that plant growth and carbon dioxide absorption (CO2), a gas with greenhouse effect, are clearly restricted by drought events, which in turn will contribute to climate change.
The use of satellite images allows us to evaluate the behaviour of vegetation in the most recent and severe drought events of 1999, 2002, 2005 and 2012. The numbers are revealing. “In 2005 and 2012, we had about 60% of the Iberian Peninsula in vegetation 'stress' for at least eight to nine months”, indicates the researcher and author of a study on this topic entitled Drought and vegetation stress monitoring in Portugal using satellite data.
Some areas of the Iberian Peninsula are most often affected by extreme drought events, such as the Alentejo. However, and according to the researcher, it is still early to talk about desertification.
Droughts and fires: A sometimes fatal combination
Droughts also have indirect effects, such as forest fires. Not surprisingly, the biggest fire seasons in Portugal occurred in 2003, coinciding with a heat wave, and in 2005, coinciding with the most severe drought of the century.
Célia Gouveia has studied, in particular, the combined effect of droughts: at the beginning of the following fire season and in the recovery of vegetation in Mediterranean ecosystems after the fires. Her study, entitled “Drought impacts on vegetation in the pre- and post-fire events over Iberian Peninsula” showed that the vegetation dynamics in the years preceding the fires have a significant influence on the severity of the damage caused by them.
From an economic standpoint, drought losses are accounted for. Data from the Portuguese Environment Agency (APA) indicate that, for instance, the estimated costs of the 2005 drought was about 290 million euros, whilst the estimated damages of the 2012 drought was about 200 million euros, mainly in terms of reduced agricultural production.
Adapting to live
With regard to drought, the future does not look blooming. Between 2071 and 2100, the EU agricultural area affected by drought is expected to increase sevenfold, reaching 700,000 km2 per year, according to the Project PESETA II. Southern Europe is expected to represent nearly 60% of the total affected area, compared to the current 30%. Of the 153 million people who will be affected by drought annually, half will be in this region.
If it is impossible to stop climate change and prevent drought, it is necessary to move forward with adaptation measures to adjust the natural and human systems to the expected effects. Agriculture is one of the systems that will have to adapt to what is coming.
To Célia Gouveia, “there must be an adjustment not only of cultivated species but also of the areas in which they are grown.” For example, some argue that a possible solution is to cultivate vineyards in the less sunny slopes. As for cereals, the solution may be to plant other cereals or adapted species. “The adaptation measures can be very harsh. We need to educate the public. It is a very long process”, she warns.
In the short term, she declares, “if we are able to monitor droughts throughout the year, we will be able to help farmers identify the most appropriate time to cultivate. It may be easier to choose species that are more resilient to drought than to change the culture from one location to another. There are some measures that could be valuable to minimise the damage and maximise the results.”
These are just some of the measures that could increase the strength and resilience of soil, vegetation, agriculture and, ultimately, the key social and economic sectors to the effects of climate change. Others may come from continuous scientific research done nationally, such as the work carried out by the QSECA project.
As part of the Mediterranean Basin, the Iberian Peninsula is considered one of the most sensitive areas to the impacts of climate change. These include the rise in temperature, and consequently of the frequency of heat waves, as well as the great variability of the average precipitation in depth pattern and of the water availability. All of these factors are associated with the increase in severe droughts. There are still many uncertainties, particularly with regard to precipitation in Portugal, as the head of QSECA emphasises.
Starting in 2013, the QSECA project aims to monitor, assess and characterise droughts recorded in the Iberian Peninsula in the past and present, through their relationship with the weather. The intention is to improve the understanding, diagnosis, and modulation of these extreme events and of their impact in the future. “We will only be able to predict what will happen in the future if we can understand what happened in the past, and what is currently happening”, she comments.
One of the objectives of QSECA is to develop information and diagnostic tools for droughts, notably through the implementation of a drought index recently developed by the research group of Vicente-Serrano (Spanish National Research Council – IPE-CSIC) integrating the project. The SPEI index - Standardized Precipitation Evapotranspiration Index- includes the effect of temperature by modelling evapotranspiration, a parameter that Célia Gouveia considered “very important” in a climate change context.
The group will also use satellite derived vegetation indices to assess the impact of drought on vegetation. The data will be disclosed not only to the scientific community but also to policy makers. “We plan to equip competent authorities with information and tools to make the right decisions”, mentions the coordinator.
Drought impacts yesterday, today and tomorrow
Droughts are not a new phenomenon. According to Célia Gouveia, data from the last 60 years indicate a “general trend of increased dryness in the Iberian Peninsula. This trend is more significant in some areas, due to the variability of precipitation and the increasing evaporative demand”.
Paleoclimatology studies developed by Spanish researchers based on lake sediments found a relationship between the existence of extreme drought in the past and the disappearance of civilisations. The results of these studies were presented recently at a workshop organised by the QSECA project in Lisbon.
While it is difficult to accurately predict all the effects of extreme events in Portugal, it is known that the drought has profound impacts on various systems, from agriculture to forests, including water resources and the national economy.
The coordinator of QSECA has studied, in particular, the effects of drought on vegetation. “In the Iberian Peninsula, there is a strong correlation between the most extreme events of drought and the activity of the vegetation”, she affirms.
Indeed, “the increase in the frequency and severity of droughts, together with heat waves, impacts the vegetation at various levels, including the variability of vegetation, the carbon balance, soil degradation, and agricultural productivity, especially cereals, which are dryland cultures that are highly dependent on rainfall. In some cases, recurring and intense droughts can even lead to the death of trees, similar to the events that occurred in some regions during the severe drought of 2012. The recovery could take years”.
As for the carbon balance, it is known that plant growth and carbon dioxide absorption (CO2), a gas with greenhouse effect, are clearly restricted by drought events, which in turn will contribute to climate change.
The use of satellite images allows us to evaluate the behaviour of vegetation in the most recent and severe drought events of 1999, 2002, 2005 and 2012. The numbers are revealing. “In 2005 and 2012, we had about 60% of the Iberian Peninsula in vegetation 'stress' for at least eight to nine months”, indicates the researcher and author of a study on this topic entitled Drought and vegetation stress monitoring in Portugal using satellite data.
Some areas of the Iberian Peninsula are most often affected by extreme drought events, such as the Alentejo. However, and according to the researcher, it is still early to talk about desertification.
Droughts and fires: A sometimes fatal combination
Droughts also have indirect effects, such as forest fires. Not surprisingly, the biggest fire seasons in Portugal occurred in 2003, coinciding with a heat wave, and in 2005, coinciding with the most severe drought of the century.
Célia Gouveia has studied, in particular, the combined effect of droughts: at the beginning of the following fire season and in the recovery of vegetation in Mediterranean ecosystems after the fires. Her study, entitled “Drought impacts on vegetation in the pre- and post-fire events over Iberian Peninsula” showed that the vegetation dynamics in the years preceding the fires have a significant influence on the severity of the damage caused by them.
From an economic standpoint, drought losses are accounted for. Data from the Portuguese Environment Agency (APA) indicate that, for instance, the estimated costs of the 2005 drought was about 290 million euros, whilst the estimated damages of the 2012 drought was about 200 million euros, mainly in terms of reduced agricultural production.
Adapting to live
With regard to drought, the future does not look blooming. Between 2071 and 2100, the EU agricultural area affected by drought is expected to increase sevenfold, reaching 700,000 km2 per year, according to the Project PESETA II. Southern Europe is expected to represent nearly 60% of the total affected area, compared to the current 30%. Of the 153 million people who will be affected by drought annually, half will be in this region.
If it is impossible to stop climate change and prevent drought, it is necessary to move forward with adaptation measures to adjust the natural and human systems to the expected effects. Agriculture is one of the systems that will have to adapt to what is coming.
To Célia Gouveia, “there must be an adjustment not only of cultivated species but also of the areas in which they are grown.” For example, some argue that a possible solution is to cultivate vineyards in the less sunny slopes. As for cereals, the solution may be to plant other cereals or adapted species. “The adaptation measures can be very harsh. We need to educate the public. It is a very long process”, she warns.
In the short term, she declares, “if we are able to monitor droughts throughout the year, we will be able to help farmers identify the most appropriate time to cultivate. It may be easier to choose species that are more resilient to drought than to change the culture from one location to another. There are some measures that could be valuable to minimise the damage and maximise the results.”
These are just some of the measures that could increase the strength and resilience of soil, vegetation, agriculture and, ultimately, the key social and economic sectors to the effects of climate change. Others may come from continuous scientific research done nationally, such as the work carried out by the QSECA project.
By: Cláudia Azevedo