The importance of climate change for a grasshopper

Our colleague Urs talks to us about the importance of mountainous areas. Specifically, the importance at times of global warming as a refuge for low-mobility insects, such as the Eurosiberian grasshopper Stethophyma grossum.

The problem of global warming for species

In times of undeniable temperature increases and observed climatic changes, changes are observed in flora (such as when mountain species rise in height), in fauna, among others detectable in the phenology of migratory birds or in the increase in their insect distribution area from more southern regions to the north, as demonstrated by the example of Trithemis kirbyi. It is a dragonfly widespread in Africa, Arabia and the subcontinent of India. In Europe, it was first observed in 2003 on the island of Sardinia (since then there have been no new records published), while in Spain it was detected for the first time in 2007 and is now being successfully reproduced. It is currently expanding in the Iberian Peninsula, in Portugal it was mentioned for the first time in 2016, in addition to detecting it already north of the Pyrenees.
However, what happens to species in our territory with more restricted mobility, such as a natural flyer such as the aforementioned dragonfly or birds. In addition, if it is an insect with a Eurosiberian distribution, which lives for ecological needs on mountainous “islands” with a climate more similar to the Atlantic (for example, lack of summer air) in the middle of a Mediterranean ocean. This avoids connectivity to other populations and their migrations.

The Grasshopper Case Stethophyma grossum

This is the case of Stethophyma grossum, large marsh grasshopper in English, which can be translated as great swamp grasshopper. This species has a EuroSiberian distribution, extending from Eastern Siberia to the northern third of the Iberian Peninsula, here reaching its south-western limit of distribution. It is found in the Cantabrian Mountains, part of the north-western Iberian System, the Pyrenees, as well as in Teruel and Guadalajara (Sierra de Albarracín and surroundings). Its distribution is characterized by a discontinuity.

Description of this “little grasshopper”

It stands out for its large size (♂ up to 25mm, ♀ up to 35-40mm) and chromatic design. It combines green (-olive), black, yellow and orange, making it one of the most attractive and conspicuous orthopterans. It inhabits, among other things, the banks of riverbeds and lakes, peat bogs, swampy and flooded areas, as well as extensive humid mowing meadows, always with the presence of Juncaceae and/or Carex plants, its source of food. Regarding its altitude distribution in Spain, there are records between 500 meters above sea level (Montes de Ordunte, Burgos) and 2,130 meters above sea level in the Catalan Pyrenees, in Andorra up to 2,350 meters above sea level.

Safe, probable or possible survival

Detecting changes in regions inhabited by species, studying the abundance of populations, the plasticity of species and their adaptations to changes are basic fields of applied faunistics. In addition, they are essential to understand ecosystem dynamics, with special importance if they are umbrella species or bioindicators.

The species Stethophyma grossum, due to its specific ecological needs; marked hygrophilous character, can be considered a bioindicator for wet/swampy habitats.

However, how can one interpret an evolution or a state of conservation, without knowing the presence of species, their distribution or abundance? And this is where the focus on this chosen species and the place chosen comes into special consideration: Stethophyma grossum in the Sierra de Albarracín and around.

The study of the distribution of this grasshopper in the Iberian Peninsula is characterized by a great lack of knowledge. Except for some more recent works (all from the new millennium) that greatly increase knowledge of their distribution, there are only a few old records, such as in the Pyrenees and some appointments in Cantabria.

More than 120 years

However, oddly enough but due to fortunate circumstances, the presence of S. grossum has been confirmed in the Sierra de Albarracín since the end of the 19th century. BOLIVAR mentioned it for Albarracín as early as 1878 and thus makes this region the one with the oldest records for Spain. In 1982 HERRERA mentioned S. grossum again for Albarracín and recent genetic studies used specimens of this species from a place near Orea (Guadalajara), a region bordering the Sierra de Albarracín.

This means that there is evidence of this EuroSiberian species for this southernmost distribution area known to date for more than 120 years. Last year, while traveling through these beautiful places, our colleague Urs cannot resist the temptation to get into some peat bogs, puddles,... stepping on all the humid meadows that came before him in search of S. grossum. He found that he is still inhabiting those mountains. He did not find many inhabited sites, but he was able to confirm their presence and promises to return next summer.

It should be noted that the high peaks of that Spanish mountainous area, with findings of this grasshopper, are very remote from other regions with the presence of the species, such as the Pyrenees or the Iberian System, with straight-line distances of about 250 km to the Pyrenees and 190 km to the Burgalesa-Soriana area respectively.

There are studies regarding the mobility and capacity for expansion of the species, and with the knowledge obtained, it can be considered practically impossible for there to be a connection between the different regions, so the concept of metapopulation is not applicable. In addition, there are no areas with possible bridging biotopes to the above-mentioned regions, for example, between the Sierra de Albarracín and the Pyrenees there is the Ebro Valley, pure Mediterranean.

In this regard, mention can be made of an observation obtained in Spain of grasshopper migrations on the back of transhumant cattle. Very interesting, but rather anecdotal, since on the one hand there are no longer those numerous transhumant herds of past times, and on the other hand, while seeds can be kept in the wool or digestive tract of cattle for days or weeks, an insect mounts for a short time.

Taking into account the fact of global warming and the changes it may cause in flora and fauna, is it important to have these records, although it is not an emblematic species but only a rare grasshopper for the Iberian Peninsula that lives on “mountainous islands” with meteorological parameters other than Atlantic features surrounded by a Mediterranean climate?

How many years can these, obviously, relict populations survive in the Sierra de Albarracín, under the threat of a galloping increase in temperatures and changes in the rainfall regime with their consequences on the habitats colonized by S. grossum?

Can taking time for observation in the Sierra de Albarracín be a good example of Citizen Science?

Well, in conclusion, the question is: can Stethophyma grossum still be observed after another 120 years, in the year 2,140, or is it doomed to extinction in that Spanish region?

The habitat (examples)