Human-mediated dispersal of seeds over long distances

Abstract

Human activities have fundamental impacts on the distribution of species through altered land use, but also directly by dispersal of propagules. Rare long-distance dispersal events have a disproportionate importance for the spread of species including invasions. While it is widely accepted that humans may act as vectors of long-distance dispersal, there are few studies that quantify this process. We studied in detail a mechanism of human-mediated dispersal (HMD). For two plant species we measured, over a wide range of distances, how many seeds are carried by humans on shoes. While over half of the seeds fell off within 5 m, seeds were regularly still attached to shoes after 5 km. Semi-mechanistic models were fitted, and these suggested that long-distance dispersal on shoes is facilitated by decreasing seed detachment probability with distance. Mechanistic modelling showed that the primary vector, wind, was less important as an agent of long-distance dispersal, dispersing seeds less than 250 m. Full dispersal kernels were derived by combining the models for primary dispersal by wind and secondary dispersal by humans. These suggest that walking humans can disperse seeds to very long distances, up to at least 10 km, and provide some of the first quantified dispersal kernels for HMD.

The problem of spatial fit in social-ecological systems: detecting mismatches between ecological connectivity and land management in an urban region

“…The movements of wetland birds within and between catchments shape the dispersal pattern of many hydrophilic plants (Amezaga et al 2002;Figuerola and Green 2002;). Wichmann (2009) demonstrated that seeds that were dispersed by wind maximally 250 m were carried by walking humans up to 10 km (cf. Auffret and Cousins 2013).…”

Using Available Information to Assess the Potential Effects of Climate Change on Vegetation in the High Arctic: North Billjefjorden, Central Spitsbergen (Svalbard)

“…The 'hot spots' usually occur under 'bird cliffs' and are enriched by nutrients and characterized by higher insulation and protected against strong winds. Another potential source of diaspores is the regular boat service during the summer, which brings about 30 tourists per day to the former settlement (Wichmann et al 2009;Hall et al 2010). …”

Feral genetically modified herbicide tolerant oilseed rape from seed import spills: are concerns scientifically justified?

“…Feral oilseed rape typically originates either from the spillage of seed during its transport to and from fields, the redistribution of seed by field equipment (Price et al, 1996;Zwaenepoel et al, 2006;von der Lippe and Kowarik, 2007b;Pivard et al, 2008a,b), or the dispersal of seed, for example by birds and mammals (von der Lippe and Kowarik, 2007a,b;Wichmann et al, 2009). Within agricultural fields, seeds can be lost through the shattering of the seed-bearing pods before and during harvest.…”

“…Seed brought in from outside could be carried by vehicles, road verge mowers, animals, or by the movement of soil for agricultural and building works (Wilkinson et al, 1995;Garnier et al, 2008;Wichmann et al, 2009). Garnier et al (2008 showed that wind turbulence behind passing vehicles locally contributed to the secondary dispersal of seed: on average, 20% of the seed was estimated to disperse over a few metres, while 80% of the seed remained at the original place.…”