AboutZoos, Since 2008


Sci­en­tists chal­lenge cur­rent the­o­ries about nat­ural habi­tats and species diversity

pub­lished 31 Decem­ber 2012 | mod­i­fied 31 Decem­ber 2012

Castle marshes nature reserveEcosys­tems and the species they con­sist of are under increas­ing pres­sure of human activ­ity. In these con­di­tions, skill­ful and intel­li­gent man­age­ment of nat­ural land­scapes is vital. A recent study pro­vides sci­en­tists and pol­icy mak­ers with impor­tant insights for the selec­tion and man­age­ment of areas for con­ser­va­tion.

How can a square meter of meadow con­tain tens of species of plants? And what fac­tors deter­mine the num­ber of species that live in an ecosys­tem? Sci­ence jour­nal has defined this as one of the 25 most impor­tant unre­solved ques­tions in sci­ence, both for its impor­tance in under­stand­ing nature and due to the value of nat­ural ecosys­tems for mankind. The value of goods and ser­vices pro­vided by nat­ural ecosys­tems is esti­mated to exceed the GDP of our planet.

For over 50 years, con­ven­tional eco­log­i­cal the­o­ries have pre­dicted that the num­ber of species that can coex­ist in a given area increases with the het­ero­gene­ity of the envi­ron­men­tal con­di­tions in the habi­tat. This premise was exam­ined in a study con­ducted by research stu­dents Omri Allouche and Michael Kalyuzhny, guided by Prof. Ronen Kad­mon from the Alexan­der Sil­ber­man Insti­tute of Life Sci­ences at the Hebrew Uni­ver­sity of Jerusalem, in col­lab­o­ra­tion with Prof. Gre­go­rio Moreno-​Rueda and Prof. Manuel Pizarro from Uni­ver­si­dad de Granada.

The researchers claim that in a het­ero­ge­neous envi­ron­ment — where there are many dif­fer­ent types of habi­tats — there are fewer resources and less suit­able area avail­able to each species, mak­ing them more vul­ner­a­ble to local extinc­tion. This leads to the hypoth­e­sis that exces­sive habi­tat het­ero­gene­ity may actu­ally reduce the num­ber of species.

This hypoth­e­sis was exam­ined using math­e­mat­i­cal mod­els and empir­i­cal analy­ses of nat­ural ecosys­tems. Its pre­dic­tions were exam­ined with a meta-​analysis of tens of datasets of plant and ani­mal species from var­i­ous local­i­ties world­wide. The results have been pub­lished online in the Octo­ber edi­tion of the Pro­ceed­ings of the National Acad­emy of Sci­ence.

Both the the­o­ret­i­cal results and the data analy­ses sup­ported the researchers’ hypoth­e­sis that habi­tat het­ero­gene­ity may increase the rate of species extinc­tions and there­fore reduce the num­ber of species that inhabit the ecosystem.

These find­ings are very impor­tant for the con­ser­va­tion of bio­di­ver­sity, since the cur­rent prac­tice is to con­serve areas of max­i­mal habi­tat het­ero­gene­ity and even to take mea­sures to increase habi­tat het­ero­gene­ity. The study shows that this con­ven­tional approach may lead to neg­a­tive results, espe­cially in the case of land­scapes of lim­ited size, which is typ­i­cal of nature reserves.

The study, Area-​heterogeneity trade­off and the diver­sity of eco­log­i­cal com­mu­ni­ties, was pub­lished in the Pro­ceed­ings of the National Acad­emy of Sci­ence. It was funded by the Israel Sci­ence Foun­da­tion and by Israel’s Min­istry of Sci­ence and Tech­nol­ogy.

(Source: The Hebrew Uni­ver­sity of Jerusalem press release, 30.12.2012)

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