A method for calculating minimum biodiversity offset multipliers — new paper by Laitila, Moilanen and Pouzols

Methods in Ecology and EvolutionJussi  Laitila, Atte Moila­nen and Fed­erico M. Pouzols have pub­lished a new paper on A method for cal­cu­lat­ing min­i­mum bio­di­ver­sity off­set mul­ti­pli­ers account­ing for time dis­count­ing, addi­tion­al­ity, and per­ma­nence” in Meth­ods in Ecol­ogy and Evo­lu­tion. Read more here and find the abstract copied below.


1.Biodiversity off­set­ting, which means com­pen­sa­tion for eco­log­i­cal and envi­ron­men­tal dam­age caused by devel­op­ment activ­ity, has recently been gain­ing strong polit­i­cal sup­port around the world. One com­mon crit­i­cism lev­elled at off­sets is that they exchange cer­tain and almost imme­di­ate losses for uncer­tain future gains. In the case of restora­tion off­sets, gains may be real­ized after a time delay of decades, and with con­sid­er­able uncertainty.

2.Here we focus on off­set mul­ti­pli­ers, which are ratios between dam­aged and com­pen­sated amounts (areas) of bio­di­ver­sity. Mul­ti­pli­ers have the attrac­tion of being an eas­ily under­stand­able way of decid­ing the amount of off­set­ting needed. On the other hand, exact val­ues of mul­ti­pli­ers are very dif­fi­cult to com­pute in prac­tice if at all possible.

3.We intro­duce a math­e­mat­i­cal method for deriv­ing min­i­mum lev­els for off­set mul­ti­pli­ers under the assump­tion that off­set­ting gains must com­pen­sate for the losses (no net loss off­set­ting). We cal­cu­late absolute min­i­mum mul­ti­pli­ers that arise from time dis­count­ing and delayed emer­gence of off­set­ting gains for a one-dimensional mea­sure of bio­di­ver­sity. Despite the highly sim­pli­fied model, we show that even the absolute min­i­mum mul­ti­pli­ers may eas­ily be quite large, in the order of dozens, and the­o­ret­i­cally arbi­trar­ily large, con­tra­dict­ing the rel­a­tively low mul­ti­pli­ers found in lit­er­a­ture and in practice.

4.While our results inform pol­icy mak­ers about real­is­tic min­i­mal off­set­ting require­ments, they also chal­lenge many cur­rent poli­cies and show the impor­tance of rig­or­ous mod­els for com­put­ing (min­i­mum) off­set mul­ti­pli­ers. The strength of the pre­sented method is that it requires min­i­mal under­ly­ing infor­ma­tion. We include a sup­ple­men­tary spread­sheet tool for cal­cu­lat­ing mul­ti­pli­ers to facil­i­tate application.

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