POLLINATORS POLLINATION AND FOOD PRODUCTION

THE ASSESSMENT REPORT ON POLLINATORS, POLLINATION AND FOOD PRODUCTION
3.1 INTRODUCTION
In recent years, the widely-publicized decline of pollinators
and its implications for global food security and natural
ecosystems has seized popular and scientific attention. Is
this widespread concern justified? This chapter presents an
overview of the trends in pollinators and pollination worldwide.
It addresses the spatial and temporal status and trends in
wild pollinators, managed pollinators, introduced invasive
pollinators and plants, the structure of pollination networks,
wild plant pollination and reproductive success, agricultural
pollinator dependence, crop pollination and yields.
This chapter focuses on the following questions: For wild
and managed pollinators, is there an on-going, long-term
decline? What changes have actually been observed (i.e.,
decline in abundance, decline in species diversity, or changes
in community composition)? What are the consequences of
these changes for the reproduction of wild plants and crop
yields? Specifically, does the evidence indicate clear spatial
or temporal trends in pollinator abundance and diversity,
changes in pollinator composition, in mean flower visitation
rates and their variability, or in pollination deficits? Moreover,
it is important to understand whether and how current trends
can be extrapolated to larger scales and new areas, or used
as the basis for predictive analyses.
In the process of pollination, there is a clear link between
flowering plants and pollinators, both of which diversified
in the mid-Cretaceous ca. 120-150 million years ago (Hu
et al., 2008). This means that there is a long evolutionary
history for the ecosystem function of pollination, which may
even predate the flowering plants (Ollerton and Coulthard,
FIGURE 3.1
2009). The first historical observation of pollinators being
important, namely affecting crop yield, includes depictions
in ancient art (Buchmann and Nabhan, 1997). Numerous
other examples have since become known, and can be
found referenced in the subsequent sections of this chapter
and in previous chapters. Without a doubt pollinators are an
essential component of biodiversity, yet relatively few studies
address the threat of (local) extinctions. Most emphasis is
on the characterisation of the interactions between plants
and pollinators (Bond, 1994). Some examples from island
systems are exceptions in this regard, where disruptions of
animal-plant interactions have been more readily quantified
(Cox and Elmqvist, 2000) and there are several documented
pollinator extinctions (Ollerton et al., 2014; Cox and
Elmqvist, 2000; Fleischer et al., 2008). Recently, examples
document regional declines and local extinctions of native
pollinators as a consequence of the international commercial
traffic in bees and plants (Stout and Morales, 2009).
Over the past 200 years, attention from academic
researchers, and to some degree the general public, has
shifted from (managed) honey bees to pollinators in general,
with a steep increase starting in the 1970s (Figure 3.1).
Concern about pollinator decline is relatively recent (Kevan,
1999; Raw, 2001; Spira, 2001; Committee on the Status
of Pollinators in North America, 2007; Williams, 1982),
but there is a growing perception among both scientists
and the general public that at least some populations and
species are declining in at least some areas. Much of this
concern comes from well-documented declines in managed
honey bee (A. mellifera) populations in North America and
Europe, as well as more recent reports of declines and even
local or global extinctions of some native bees, such as
Temporal trend in the use of the terms ‘pollinator’, ‘honeybee’ and ‘honey bee’ generated using Google Ngram. This shows the trend
in the currently databased collection of Google Books between the years 1800 and 2008 (percentage of all books published in the
USA in English that contain the designated term). Note the recent (post 2000) switch to the term ‘pollinator’ appearing more frequently
in publications than ‘honey bee’. This may be attributed to the increased number of publications that are focused on the breadth and
diversity of pollinators as providers of an essential ecosystem function.
155
3. THE STATUS AND TRENDS IN POLLINATORS
AND POLLINATION
0.0000400%
0.0000350%
0.0000300%
0.0000250%
honey bee
0.0000200%
0.0000150%
honey bee
pollinator
0.0000100%
0.0000050%
0.0000000%
1800 1820 1840 1860 1880 1900 1920 1940 1960 1980 2000