Subject: | |
From: | |
Reply To: | |
Date: | Tue, 15 Nov 2022 11:03:28 -0600 |
Content-Type: | text/plain |
Parts/Attachments: |
|
|
>If correct, would that not have been reflected in both the size of our
colonies (assuming queens are still laying at the same rate) and our honey
crop.
From the study - and they are clear about only including US data:
*... the median lifespan of caged honey bees has been declining in the US
since the 1970’s, from an average of 34.3 days to 17.7 days. In response to
this, we again turned to historical record and found a relationship between
this trend and a decline in the average amount of honey produced per colony
per year in the US over the last 5 decades.The average median lifespan of
caged bees in the 1970’s was 34.3 (± 1.5) days and has reduced to 17.7 (±
2.0) days 50 years later (Table 1).The resulting parsimonious model of 46
trials across 25 publications suggests the median lifespan of US worker
bees has declined at a rate of 0.22 days per year since 1970....active
season bees in the 1960’s had a mortality rate of 0.015 (0.5 divided by an
average lifespan of 32.5 days), while the mortality rate of the past decade
is observed to be 0.030 (0.5 divided by an average median lifespan of 17.7
days).When current-day bee lifespans and Varroa impacts are used in the
model, it predicts decreases in colony survival that, when extrapolated to
the operational level, predict cyclical operational losses that fit well
within the range estimated in US beekeeping operations over the last 14
years (Supplementary Fig. S1).Comparing the two mortality rates as a
parameter in the BEEHAVE model, we found that the decreased median life
spans observed in the 2010’s predict a 26% decrease in honey production and
a 29% decrease in maximum population size, on average. Model replicates
using the 1960’s longevity data predicted no colony mortality over 10 years
if external threats like Varroa were perfectly controlled. By introducing
Varroa as a problem, the same mortality rate predicts colonies would live
an average of 4.6 years. This average decreases by 33%, to 3.1 years when
worker bee mortality rates are increased to current estimates and Varroa is
imperfectly controlled (Fig. 5).In the highest loss regimes (in-hive bee
mortality rates of 0.0068 or more, Supplementary Table S1), cohorts lost
100% of their colonies in 5 years without replacing dead colonies, an
annual loss rate of 20% is predicted. When dead colonies are replaced
annually, the average annual rate of loss increases to 33%, a figure close
to the average winter loss rate reported in the US over the last 14 years
(Supplementary Fig. S1).*
***********************************************
The BEE-L mailing list is powered by L-Soft's renowned
LISTSERV(R) list management software. For more information, go to:
http://www.lsoft.com/LISTSERV-powered.html
|
|
|