LICCI Science

The potential of local observations as a proxy for the study of climate extremes: relating farmers´ knowledge with tree rings in central Spain

The LICCI collaborator Maria Arredondo has recently defended her MSc thesis, under the supervision of LICCI Core Team member André Braga Junqueira and of Dr. Pieter Zuidema (Wageningen University, The Netherlands). Her research aimed to explore the potential of local observations as a proxy for the study of climate extremes, and to relate farmers´ knowledge on extreme events with climatic records imprinted in tree rings.

Problem statement

One of the main concerns related to climate change is the predicted increase in the occurrence of extreme climatic events. These extremes, however, are often studied based on a purely climatological definition, which presents three main problems: (1) it does not include the effects such events have on (agro-) ecosystems, nor (2) on people depending on them and (3) it relies on instrumental climate data, which is often scarce or of poor quality, especially when studying longer time periods. Aiming to tackle these problems, Maria investigated the occurrence of extreme events based on farmers´ own perceptions of these events and of their impacts. Besides, she looked into how farmers´ perceptions of extreme events matched the past variations in climate recorded in dendrochronological datasets (i.e., tree rings), which often provide a local and long-term record of climatic oscillations.

To do so, María interviewed vine and cereal farmers, with varying levels of previous agricultural experience, in La Alcarria (Central Spain), a region with a strong agricultural tradition, where about a third of the land is dedicated to (mostly rainfed) agriculture.  

She found that farmers with more agricultural experience recalled a higher number of past extreme events, calling the attention on the need of focusing on more experienced people to enhance the contribution of LEK to climate research. Moreover, even though cereal and vine farmers recalled a similar total number of events, cereal farmers mentioned drought events more often than vine farmers, likely because droughts affect cereal farmers more directly than vine farmers. This highlights the importance of considering the diversity of farmers and their livelihood activities to understand the impacts of climate change more thoroughly.

Finally, when comparing local knowledge with dendrochronological data, Maria found associations between farmers´ recalls of extreme events and dendrochronological data, but the years mentioned most often as extremely rainy or dry by farmers did not fully match those belonging to the thickest and thinnest tree rings. This indicates that climatic events considered as ´extreme´ and that have substantial impacts for local livelihoods may not be the same as those recorded as ´extreme´ in tree rings. Farmers often recalled relatively short-term events that occurred in specific moments of the year and that had substantial impacts in their crops. For example, cereal farmers referred often to rainfall on the first weeks of April, while vine farmers referred to rains in April/May and September as the most relevant periods for their crops. These short-term events may not be recorded in tree rings, as tree growth responds rather to longer-term variations in water availability. Taken together, these results indicate that initiatives targeting mitigation and adaptation to climate change should go beyond climatic proxies and pay attention to local knowledge to thoroughly understand the occurrence and trends in extreme climatic events and their impacts in local livelihoods. Maria is grateful to the farmers from La Alcarria for kindly sharing their insights, knowledge, and inspiration.

“La Alcarria desde Trijueque.” by fcuencadiaz is licensed under CC BY-NC-SA 2.0