>an important point lost on most people who discuss the "decline of
pollinators" is that the number of colonies in the US decline[d] from 6
million to 2.5 million with no negative effect.
> Average decadal yields of 10 crops for six complete decades (1945 through
2005) and the most recent partial decade (2005 through 2010 or 2011,
depending upon data availability) are presented in Table 2. The results
indicate that the yield in the most recent decade is the highest in all
considered crops except for apple. For the crops that are less dependent on
honey bee pollination (corn, wheat, peanut, soybean, tomato), yield has
increased in almost every decade from 1945
==============
I don't disagree in general terms with the point being made, but the paper
quoted in support of it is very weak. Put that to one side. In the paragraph
quoted the next sentence reads "For crops highly dependent on pollinators,
yield increase was inconsistent through the decades" and goes on later to
argue (in the Conclusion) "As might be expected, the decline in pollinator
population has also caused a slower and more unstable yield increase for the
crops that are dependent on pollinators, Analysis of the yield reduction of
selected crops that resulted from pollination decline(!) demonstrated a
substantial economic loss". I'd paraphrase that to mean, 'inadequate
pollination created a yield lower that it could have been.' This is a
popular argument, and would be a "negative effect", if it could be shown.
Now, I subsidize my beekeeping working in a post-harvest operation packing
what I would say is a crop with significant pollinator dependency. Year on
year yields vary noticeably, but pollination would be the last thing on my
mind if I had to explain why. Assuming pests and nutrition are controlled
(they are, and don't show much year to year change), then I think about the
following:
Vine age and size, vines age, old vines can carry a heavier crop than young,
small vines, but a plant can get too big. Pruning in the previous year,
selecting enough of the right kind of fruiting canes. Can I afford to buy an
'expert' pruning gang? Tying in the 'right' number and quality of buds on
canes in winter. The degree of winter chilling, the weather around bud
burst, the use and timing of chemical dormancy-breakers. Pruning, bud
thinning, and flower thinning, to meet this year's market preference for
fruit size and earn top-dollar. Deciding about early, (lower yield) or late
targeted crops (higher yield), which depends on changing incentive and risk
payments, and on how risk-adverse the grower(s) (and his bankers) are. After
fruit set, fruit thinning. How much will it cost, how necessary is it, how
much will the packhouse charge for handling undersize? This has to be
recalculated every year (like everything). The accumulation of dry matter
and brix changes towards harvest are weather dependent and may change
planned harvest timing, so the cost/benefit analysis has to be redone,
factors like impending frosts and disease management have a bearing on when
the harvest will happen, and when payment will start. An 'early' crop picked
late may incur spoilage and have a lower yield, or the extra growing time
may let small fruit grow to a saleable size. Fruit crops are 'managed'
according to the inventory chain - it's far cheaper to avoid over-supply
(and the consequent price crash) by dropping the fruit in-orchard rather
than after processing costs have been incurred, just ask a grape grower.
And, as I grow more than one crop or variety, I will spend more of my budget
on the crop that is likely return most that year, and I may get it wrong and
have a good yield on a poorly paid variety!
I could go on, but you get the idea, The decisions we make that alter the
yield figures which Sinnathamby et al (and others) use in their studies have
nothing to do with pollination, and everything to do with business, risk,
and the weather. If pollination did matter, its contribution is masked by
much bigger decisions. As far as I can see these kind of decisions always
apply to managed perennial crops, and it's the perennials that seem to make
up most of the 'pollinator dependent' crops. I suggest the yield from a
managed crop is substantially determined by the market for it, and there
ain't much biological about it. Am I wrong?
Ref:
Sinnathamby, S., Assefa, Y., Granger, A. M., Tabor, L. K., & Douglas-Mankin,
K. R. (2013). Pollinator Decline: US Agro-Socio-Economic Impacts and
Responses. Journal of Natural and Environmental Sciences, 4(1), 1-13.through
2010.
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