Data from: More milkweed in farmlands containing small, annual crop fields and many hedgerows

See Martin et al. (2021, Agriculture, Ecosystems and Environment 319: 107567, https://doi.org/10.1016/j.agee.2021.107567) for full description of methods.
Abstract: Milkweed has declined substantially, with over 80% declines
in some agricultural regions. This threatens monarch butterfly (Danaus
plexippus) persistence, because monarch larvae feed solely on milkweed. Thus
conservation actions are needed to enhance the availability of milkweed,
particularly in agricultural landscapes. Conservation actions to date have
largely focused on reducing intensive agricultural practices, mainly use of
herbicides. However, research suggests that landscape-scale alteration of the
cropped portion of an agricultural landscape (the "farmland"), for
example, to reduce crop field sizes, can benefit herbaceous plants such as
milkweed. Here we collected data on milkweed occurrence and cover in
agricultural landscapes in Ontario, Canada, capturing variability in milkweed
from field edge to interior by sampling in the interior and along the edges of
68 crop fields. We used these data to evaluate the relative effects of farming
practices within the sampled field (e.g. herbicide, fertilizer use) on milkweed
versus the effects of mean field size, crop diversity, hedgerow cover, and the proportion
of farmland in annual crops in the surrounding landscape. Additionally, we
evaluated the effects of these variables on the cover of other herbaceous
plants, to identify which—if any—could benefit milkweed without increasing
overall weed cover. We found more milkweed at sites surrounded by landscapes
with smaller crop fields, lower crop diversity, and higher cover of annual
crops. Milkweed was more likely to occur at sites surrounded by landscapes with
more hedgerows. These landscape-scale effects on milkweed were often larger
than those of within-field farming practices. Importantly, we found that most
variables had opposite effects on milkweed relative to other plants. Thus,
altering the landscape to benefit milkweed does not imply an increase in weed
cover.