Concave trade-off curves between crop production and taxonomic, functional and phylogenetic diversity of birds

Abstract

In a context of land scarcity, food production and biodiversity conservation objectives compete for land. The shape of the relationship between these two objectives may be helpful to inform decision-making. However, the metrics used to evaluate this relationship have so far been restricted to species abundances and species richness, which give no information on possible consequences on ecosystem functioning or on evolution history. Indeed, the shapes of the relationship between food production and other diversity facets, such as functional diversity and phylogenetic diversity, have rarely been studied. We considered 3 diversity facets: taxonomic diversity, functional diversity and phylogenetic diversity. For each facet, several biodiversity metrics have been proposed. The objective of this work was to investigate whether the shape of the trade-off curve between food production and biodiversity metrics depended on the considered facet of biodiversity. Using data from the national agricultural statistics, we computed edible energy from crops and from livestock on a nation-wide gradient covering French agroecosystems. Using bird observation data provided by the French Breeding Bird Survey (FBBS), we computed 9 (3 for each facet) biodiversity metrics in 516 different sites of the FBBS. The trade-off curves were then computed using additive mixed models. All metrics decreased along a crop production gradient. For functional and taxonomic diversity metrics, the slope was steeper at high levels of production, suggesting that actions aiming at increasing local taxonomic or functional diversity may be more efficient in regions with highest crop production, if restoration follows the same trajectory as biodiversity loss. The decrease was steeper for functional diversity than for taxonomic diversity, suggesting that agriculture can reduce the functional diversity of birds more than their taxonomic diversity.