Limited potential for bird migration to disperse plants to cooler latitudes

Climate change is forcing the redistribution of life on Earth at an
unprecedented velocity. Migratory birds are thought to help plants to
track climate change via long-distance seed dispersal. However, seeds may
be consistently dispersed towards cooler or warmer latitudes depending on
whether a plant species fruiting period coincides with the northward or
southward migrations. Here we assess the potential of plant communities to
keep pace with climate change via long-distance seed dispersal by
migratory birds. To do so, we combine phenological and migration
information with data on 949 seed-dispersal interactions between 46 bird
and 81 plant species from 13 woodland communities across Europe. While
most plant species (86%) in these communities are dispersed by birds
migrating south, only 35% are dispersed by birds migrating north, a subset
phylogenetically clustered in lineages with fruiting periods that overlap
with the spring migration. Moreover, only a few Palearctic migrant species
provide most of this critical dispersal service northwards. The potential
of migratory birds to assist a small non-random sample of plants to track
climate change latitudinally is expected to strongly influence the
formation of novel plant communities, thereby affecting their ecosystem
functions and community assembly at higher trophic levels.