Welcome

Whether an ani­mal or plant com­mu­nity remains sta­ble despite exter­nal impacts does not depend on bio­log­i­cal diver­sity alone: asyn­chrony across the species is also a cru­cial fac­tor. The more the species in an ecosys­tem fluc­tu­ate in their evo­lu­tion over time, the less they are likely to fal­ter. As a result, diver­sity takes sec­ond place in terms of the fac­tors to be con­sid­ered in the con­text of ecosys­tem sta­bil­ity. A team of sci­en­tists spear­headed by the Tech­ni­cal Uni­ver­sity (TU) Munich and TU Darm­stadt have pub­lished these find­ings on 12 Feb­ru­ary in the jour­nal “Nature Communications”.

The abun­dance of species is sub­ject to nat­ural vari­a­tions (dot­ted lines). The mean vari­a­tion of the entire com­mu­nity fluc­tu­ates much more if the indi­vid­ual species are syn­chro­nous. In con­trast, if the abun­dance of species varies asyn­chro­nously, the abun­dance of the com­mu­nity is very sta­ble.
Image credit: TUM/​Goss­ner.The abun­dance of species, that is their fre­quency, is sub­ject to nat­ural vari­a­tions over the course of time. These vari­a­tions are indi­cated here as dot­ted lines. The mean vari­a­tion of the entire com­mu­nity fluc­tu­ates much more if the indi­vid­ual species are syn­chro­nous with each other.
Image credit: TUM/​Goss­ner.

The long-​term func­tion­ing of ecosys­tems depends on the sta­bil­ity of their species com­mu­ni­ties, as these ensure the func­tion­ing of the entire sys­tem life cycle. How­ever, land use by humans causes a reduc­tion of the num­ber of species in many ecosys­tems. Accord­ingly, when it comes to con­serv­ing species diver­sity and pro­vid­ing sus­tain­able pro­tec­tion for nat­ural resources, the sta­bil­ity of such ani­mal and plant com­mu­ni­ties is the main goal of nature con­ser­va­tion and ecosys­tem man­age­ment. In prin­ci­ple, higher species diver­sity and greater asyn­chrony can increase the sta­bil­ity of the species com­mu­nity. But if land use is inten­si­fied or changed, which of these fac­tors — species diver­sity or asyn­chrony — is more important?

The effect of land use
For their study, the researchers eval­u­ated over 2,600 species rang­ing from insects and spi­ders, to birds and bats and through to herba­ceous grasses over a period of six years. Data from 150 forests and 150 pas­tures and mead­ows located in three regions in Ger­many were col­lated. “The results show that a change in the use of a land­scape, for exam­ple when a man­aged for­est is con­verted into grass­land, desta­bi­lizes the ani­mal and plant com­mu­nity,” explains Dr. Mar­tin Goßner from the Ter­res­trial Ecolol­ogy Research Group at the TU Munich.

“Sim­i­larly, the inten­si­fi­ca­tion of land use results in the desta­bi­liza­tion of the ani­mal and plant com­mu­nity and this, in turn, impairs the entire ecosys­tem,” adds Dr. Nadja Simons (also from the TU Munich). Ani­mal com­mu­ni­ties pre­sented a stronger reac­tion here than their plant coun­ter­parts. The most severe reac­tion by far was observed among birds and bats, which can there­fore be seen as indi­ca­tors of land-​use intensity.

The more diverse the species, the more sta­ble the ecosys­tem
Sci­en­tists have long hypoth­e­sized that bio­di­ver­sity is of crit­i­cal impor­tance to the sta­bil­ity of nat­ural ecosys­tems and their abil­i­ties to pro­vide ecosys­tem ser­vices. This assump­tion has just recently been proven in a study of which the find­ings have been pub­lished online on 13 Jan­u­ary in the jour­nal Nature.

Prof. Nico Blüth­gen, lead author, Depart­ment of Biol­ogy, TU Darm­stadt, Germany »

In addi­tion to the diver­sity of species being impor­tant for the sta­bil­ity of ecosys­tems the new insights gained in the recent study are that the asyn­chrony of the species is impor­tant as well. In fact, the extent to which the asyn­chrony of the species can increase the sta­ble inter­play of ani­mals and plants in an ecosys­tem is new. Nico Blüth­gen says, “We can com­pare it to the stock exchange, where risk-​averse investors are encour­aged not to put all their eggs in one bas­ket and to cre­ate a port­fo­lio of dif­fer­ent secu­ri­ties instead. This is referred to as the port­fo­lio effect. And, just as in nature, in order to cush­ion the impact of fluc­tu­a­tions in the invest­ments over time, it is impor­tant that the port­fo­lio not only con­tains a lot of invest­ments but also dif­fer types of invest­ments.” Asyn­chrony thus assumes a key role in the inter­ac­tion between diver­sity and sta­bil­ity. The sci­en­tists plan to inves­ti­gate the fac­tors that lead to greater asyn­chrony in fur­ther studies.

This joint project by sev­eral research groups was the most com­pre­hen­sive study on the topic of sta­bil­ity to date and was car­ried out in the con­text of the “Bio­di­ver­sity Explorato­ries” research alliance. This alliance is funded by the Deutsche Forschungs­ge­mein­schaft (DFG, Ger­man Research Foun­da­tion). One of its express aims is to facil­i­tate long-​term stud­ies of this kind, as impacts on the sta­bil­ity of ecosys­tems can only be stud­ied effec­tively from a long-​term perspective.

(Source: Tech­nis­che Uni­ver­sität München press release, 12.02.2016)

---