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Just came across this paper, which is mildly hopeful in the sense
that there is a backup for many (but not all) plants:<br>
<br>
Non-bee insects are important contributors to global crop
pollination<br>
<a class="moz-txt-link-freetext" href="http://www.pnas.org/content/early/2015/11/24/1517092112.full.pdf">http://www.pnas.org/content/early/2015/11/24/1517092112.full.pdf</a><br>
<a class="moz-txt-link-freetext" href="http://www.pnas.org/content/early/2015/11/24/1517092112.abstract">http://www.pnas.org/content/early/2015/11/24/1517092112.abstract</a><br>
<blockquote type="cite">Wild and managed bees are well documented as
effective pollinators of global crops of economic importance.
However, the contributions by pollinators other than bees have
been little explored despite their potential to contribute to crop
production and stability in the face of environmental change.
Non-bee pollinators include flies, beetles, moths, butterflies,
wasps, ants, birds, and bats, among others. Here we focus on
non-bee insects and synthesize 39 field studies from five
continents that directly measured the crop pollination services
provided by non-bees, honey bees, and other bees to compare the
relative contributions of these taxa. Non-bees performed 25–50% of
the total number of flower visits. Although non-bees were less
effective pollinators than bees per flower visit, they made more
visits; thus these two factors compensated for each other,
resulting in pollination services rendered by non-bees that were
similar to those provided by bees. In the subset of studies that
measured fruit set, fruit set increased with non-bee insect visits
independently of bee visitation rates, indicating that non-bee
insects provide a unique benefit that is not provided by bees. We
also show that non-bee insects are not as reliant as bees on the
presence of remnant natural or seminatural habitat in the
surrounding landscape. These results strongly suggest that non-bee
insect pollinators play a significant role in global crop
production and respond differently than bees to landscape
structure, probably making their crop pollination services more
robust to changes in land use. Non-bee insects provide a valuable
service and provide potential insurance against bee population
declines. </blockquote>
<br>
<blockquote type="cite">
<div class="executive-summary">
<h2 class="">Significance</h2>
<p id="p-4">Many of the world’s crops are pollinated by insects,
and bees are often assumed to be the most important
pollinators. To our knowledge, our study is the first
quantitative evaluation of the relative contribution of
non-bee pollinators to global pollinator-dependent crops.
Across 39 studies we show that insects other than bees are
efficient pollinators providing 39% of visits to crop flowers.
A shift in perspective from a bee-only focus is needed for
assessments of crop pollinator biodiversity and the economic
value of pollination. These studies should also consider the
services provided by other types of insects, such as flies,
wasps, beetles, and butterflies—important pollinators that are
currently overlooked. </p>
</div>
</blockquote>
<br>
<pre class="moz-signature" cols="72">--
Anders Sandberg
Future of Humanity Institute
Oxford Martin School
Oxford University</pre>
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