AboutZoos, Since 2008


Her­bi­vores can help halt bio­di­ver­sity loss due to nitro­gen fertilisers

pub­lished 23 March 2014 | mod­i­fied 23 March 2014

Intro­duc­ing rab­bits, deer and kan­ga­roos to grass­lands can off­set nitro­gen pol­lu­tion and help reduce bio­di­ver­sity loss, accord­ing to new research.

Rabbit in spring grassTwo wrongs may not make a right. But when it comes to grass­land plant species diver­sity, it just might. Two impacts often con­trolled by humans — being fer­tilised and being eaten — can com­bine to the ben­e­fit of bio­di­ver­sity, accord­ing to an inno­v­a­tive inter­na­tional study led by researchers Eliz­a­beth Borer and Eric Seabloom, both from the Uni­ver­sity of Minnesota.

The find­ings, pub­lished online on 9 March in Nature in advance of print pub­li­ca­tion, are impor­tant in a world where humans are chang­ing both her­bi­vore dis­tri­b­u­tion and the sup­ply of nutri­ents like nitro­gen or phos­pho­rus, and where under­stand­ing the inter­play among nutri­ents, her­bi­vores and plant growth is crit­i­cal to our capac­ity to feed a grow­ing human pop­u­la­tion and pro­tect threat­ened species and ecosystems.

To con­duct the study, Borer and Seabloom enlisted the help of the Nutri­ent Net­work, or Nut­Net. Nut­Net sci­en­tists at 40 sites on six con­ti­nents set up research plots with and with­out added fer­tiliser and with and with­out fences to keep out the local her­bi­vores such as deer, kan­ga­roos, sheep or zebras. Every year since then, they have mea­sured the amount of plant mate­r­ial grown, light reach­ing the ground, and num­ber of species of plants grow­ing in the plots.

Our new study sug­gests that the rel­a­tively sim­ple mea­sure of intro­duc­ing her­bi­vores to cer­tain areas could make a dif­fer­ence. We hope that ulti­mately this strat­egy could be widely adopted as part of con­ser­va­tion efforts to safe­guard biodiversity
Mick Craw­ley, co-​author, Depart­ment of Life Sci­ences, Impe­r­ial Col­lege London »

When the researchers com­pared data across the 40 study sites, they found that fer­til­is­ing reduced the num­ber of plant species in the plots as species less able to tol­er­ate a lack of light were lit­er­ally over­shad­owed by fast-​growing neigh­bours. On both fer­tilised and unfer­tilised plots, where removal of veg­e­ta­tion by her­bi­vores increased the amount of light that struck the ground, plant species diver­sity increased. And these results held true whether the grass­land was in Min­nesota, Argentina or China, and whether the her­bi­vores involved were rab­bits, sheep, ele­phants or some­thing else. Although her­bi­vores that had the great­est impacts were hoofed mam­mals such as cat­tle, mar­su­pi­als such as kan­ga­roos, and rab­bits. While her­bi­vore impacts were great­est in sites with a cool dry sea­sonal cli­mate, or warm and con­stant tem­per­a­tures, sug­gest­ing that the cli­mate plays an impor­tant role.

“Bio­di­ver­sity ben­e­fits humans and the envi­ron­ments that sus­tain us. Under­stand­ing how human actions con­trol bio­di­ver­sity is impor­tant for main­tain­ing a healthy envi­ron­ment,” says Borer. “What this sug­gests is that these two impacts, which are ubiq­ui­tous glob­ally, com­bine with changes in light avail­abil­ity at the ground level, and that appears to be a big fac­tor in main­tain­ing or los­ing bio­di­ver­sity in grass­lands. In short, where we see a change in light, we see a change in diversity.”

The find­ings add a key piece to the puz­zle of how human impacts affect prairies, savan­nahs, alpine mead­ows and other grass­lands. Bio­di­ver­sity plays an impor­tant role in how resilient com­mu­ni­ties of plants and ani­mals are in the face of change. By show­ing how fer­til­i­sa­tion, graz­ing, and bio­di­ver­sity are linked, the research moves us one step closer to under­stand­ing what we can do to help keep grass­land ecosys­tems and all of the ser­vices they pro­vide healthy and thriv­ing in a chang­ing world.

“Global pat­terns of bio­di­ver­sity have largely defied expla­na­tion due to many inter­act­ing, local dri­ving forces,” says Henry Gholz, pro­gramme direc­tor in the National Sci­ence Foundation’s (NSF) Divi­sion of Envi­ron­men­tal Biol­ogy, which funded the coor­di­na­tion of this research. “These results show that grass­land bio­di­ver­sity is likely largely deter­mined by the off­set­ting influ­ences of nutri­tion and graz­ing on light cap­ture by plants.”

(Source: Uni­ver­sity of Min­nesota news release, 05.03.2014; Impe­r­ial Col­lege Lon­don news release, 10.03.2014)

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