New research demonstrates high value 'injurious weeds' can bring to pollinators

Date:
March 8, 2022
Source:
University of Sussex
Summary:
New research compares the biodiversity value of plants classed as
'injurious weeds' against those stipulated by DEFRA for pollinator
targeted agri-environmental options. The findings show that the
abundance and diversity of pollinators visiting weed species are
far higher than DEFRA recommended plants.



FULL STORY ==========================================================================
A new study by researchers at the University of Sussex, funded by Rowse
Honey Ltd, has demonstrated that weeds are far more valuable in supporting biodiversity than we give them credit for.


==========================================================================
Dr Nicholas Balfour and Professor Francis Ratnieks compared the
biodiversity value of plants classified as 'injurious weeds' with those stipulated by the Department for Environment, Food and Rural Affairs
(DEFRA) for pollinator targeted agri-environmental options, such as red
clover and wild marjoram.

Their findings, published in the Journal of Applied Ecology, show that
the abundance and diversity of pollinators visiting weed species are
far higher than DEFRA recommended plants.

In the UK, five species of native wildflowers are classified as
"injurious" in the 1959 Weeds Act. Three of them are frequently visited
by many species of bees and other insects -- ragwort (Jacobaea vulgaris)
and two thistles (Cirsium arvense, C. vulgare). The other two are docks
(Rumex crispus and R.

obtusifolius), whose flowers are mainly wind-pollinated.

Dr Balfour and Professor Ratnieks conducted a field study in East Sussex
where they quantified and identified insects visiting three of these
species -- the flowers of ragwort, thistles, and other wildflowers,
including those recommended by DEFRA -- growing in six pasture or
ex-pasture sites.

Their results, which found that pollinators were visiting weed species
in higher numbers than DEFRA recommended plants, were mirrored by a
subsequent analysis of scientific literature.



==========================================================================
In the Database of Pollinator Interactions, four times as many
pollinator species and five times more conservation-listed species have
been recorded visiting the three insect-pollinated weeds. Of the 387
plant species analysed in the database, in terms of pollinator species recorded, the weeds were ranked 4th (C. arvense), 6th (J. vulgaris),
and 13th (C. vulgare). Similarly, the Database of Insects and their Food Plantsshowed that twice as many herbivorous insect species are associated
with the five weed species.

Dr Nicholas Balfour, Post-Doctoral Researcher at the Laboratory of
Apiculture and Social Insects (LASI) at the University of Sussex, said:
"There now exists a substantial body of evidence which shows that weeds
are a vitally important resource for pollinators.

"The three insect-pollinated species have open flowers that allow access
to a wide variety of pollinator species, and they produce, on average,
four times more nectar sugar than the DEFRA recommended plant species.

"Pollinators are crucial to maintaining global biodiversity, ecosystem resilience and agricultural output. However, there are significant
concerns about pollinator declines and the long-term decline of flowers
in our landscapes is considered a key factor.

"We appreciate that agricultural weeds can cause yield losses in arable
and pastureland. However, we've shown that they can also be of great
value to both flower-visiting and herbivorous insects -- and shouldn't be underestimated when it comes to supporting our natural biodiversity."
Freedom of information requests to public bodies such as councils,
Natural England and Highways England indicated that circa -L-10 million
per year is spent controlling injurious weeds.



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The majority of local councils indicated that they actively control
ragwort, thus classing it in the same bracket as invasive, non-native
species such as Japanese knotweed (Reynoutria japonica), likely due to
the Ragwort Control Bill 2003.

Dr Balfour added: "It is alarming that the many public bodies are using
tax- payers' money and volunteers to actively remove ragwort. This
plant was found to support the most conservation-listed insect species
in our study.

"The implementation of the Ragwort Control Bill probably deserves
greater scrutiny, especially given that the evidence underpinning it
is questionable.

"Our results clearly show that weeds have an underappreciated value
in supporting our natural biodiversity. Unfortunately, current UK
agricultural policy encourages neither landsparing for, nor landsharing
with, weeds." Francis Ratnieks, Professor of Apiculture at the Laboratory
of Apiculture and Social Insects (LASI) at the University of Sussex said:
"Many common native plant species valuable to wildlife conservation
are, unfortunately, underappreciated. Here we show the importance
of ragwort and thistles to flower-visiting insects. Previously LASI
has shown the importance of bramble and ivy, plants which are often
referred to in negative terms such as thugs or parasites." The authors
are now calling for policymakers to take another look at how existing
policies are implemented and reconsider the role of weeds in future agri-environmental policy. The Environmental Land Management Scheme,
which is to be rolled out for English farmers by the end of 2024, will
largely replace the schemes currently available under the EU Common Agricultural Policy. The authors are hopeful that this policy will provide sufficient directives and financial incentives to persuade land managers
to tolerate injurious weeds, while taking into account the challenges
facing different stakeholders and the balance of practicality and cost,
as well as the benefits to the natural world of tolerating weeds.

Rowse Honey Ltd.provided funding.


========================================================================== Story Source: Materials provided by University_of_Sussex. Original written
by Stephanie Allen. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Nicholas J. Balfour, Francis L. W. Ratnieks. The disproportionate
value
of `weeds' to pollinators and biodiversity. Journal of Applied
Ecology, 2022; DOI: 10.1111/1365-2664.14132 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/03/220308102812.htm

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