Being a tree crop increases the odds of experiencing yield declines irrespective of pollinator dependence

AIZEN, M. A.; GLEISER, G.; KITZBERGER, T. A.; MILLA, R.

Peer Community in Ecology

Peer Community in

Año: 2023

Crop yields, i.e. harvestable production per unit of cropland area, are in decline for a numberof crops and regions, but the drivers of this process are poorly known. Global decreases inpollinator abundance and diversity have been proposed as a major driver of yield declinesin crops that depend on animals, mostly bees, to produce fruits and seeds. Alternatively,widespread tree mortality has been directly and indirectly related to global climate change,which could also explain yield decreases in tree crops. As tree crops are expected to bemore dependent on pollinators than other crop types, disentangling the relative influenceof growth form and pollinator dependence is relevant to identify the ultimate factors drivingyield declines. Yield decline, defined here as a negative average annual yearly change inyield from 1961 to 2020, was measured in 4270 time series, involving 136 crops and 163countries and territories. About one-fourth of all time series showed declines in crop yield,a characteristic associated with both high pollinator dependence and a tree growth form.Because pollinator dependence and plant growth form were partially correlated, we disentangledthe effect of each of these two predictors using a series of generalized linear mixedmodels that evaluated direct and indirect associations. Our analyses revealed a stronger associationof yield decline with growth form than with pollinator dependence, a relationshipthat persisted after partialling out the effect of pollinator dependence. In particular, yield declineswere more common among tree than herbaceous and shrub crops in all major regionsbut in Africa, a continent showing a high incidence of yield declines irrespective of growthform. These results suggest that pollinator decline is not the main reason behind crop productivityloss, but that other factors such as climate change could be already affecting cropyield.