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Guest essay by Eric Worrall
Despite the fact tropical countries do just fine controlling agricultural weeds, computer models suggest global warming will cause weeds to be a big problem in the USA, though unusually for a climate study the authors admit there are serious limitations to their modelling technique.
Global warming will boost agriculture weed threat
Date: June 2, 2020
Source: Flinders UniversitySummary:Invasive weeds pose a significant threat to global agriculture productivity — and their threat will become more pronounced if the Earth’s climate is affected by increased greenhouse gas concentration, according a climate researcher.
Working with computer models to predict the likely impact of climate change on invasive weed propagation, Dr Farzin Shabani from Flinders University’s Global Ecology Lab found a likely increase in areas of habitat suitability for the majority of invasive weed species in European countries, parts of the US and Australia, posing a great potential danger to global biodiversity.
In predicting the impact of climate change on current and future global distributions of invasive weed species, Dr Shabani also found that existing attempts to eradicate invasive populations are inadequate.
Dr Shabani and an international team of researchers investigated 32 globally important Invasive Weed Species to assess whether climate alteration may lead to spatial changes in the overlapping of specific IWS globally.
“We aimed to evaluate the potential alterations — whether that be a gain, loss or static — in the number of potential ecoregion invasions by IWS, under climate change scenarios,” says Dr Shabani. “We utilised all possible greenhouse gas concentration to examine a range of possible outcomes.”
The paper — Invasive weed species’ threats to global biodiversity: Future scenarios of changes in the number of invasive species in a changing climate, by Farzin Shabani, Mohsen Ahmadi, Lalit Kumar, Samaneh Solhjouy-fard, Mahyat Shafapour Tehrany, Fariborz Shabani, Bahareh Kalantar and Atefeh Esmaeili — has been published in the journal Ecological Indicators.
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The abstract of the study;
Invasive weed species’ threats to global biodiversity: Future scenarios of changes in the number of invasive species in a changing climate
Invasive weed species (IWS) threaten ecosystems, the distribution of specific plant species, as well as agricultural productivity. Predicting the impact of climate change on the current and future distributions of these unwanted species forms an important category of ecological research. Our study investigated 32 globally important IWS to assess whether climate alteration may lead to spatial changes in the overlapping of specific IWS globally. We utilized the versatile species distribution model MaxEnt, coupled with Geographic Information Systems, to evaluate the potential alterations (gain/loss/static) in the number of potential ecoregion invasions by IWS, under four Representative Concentration Pathways, which differ in terms of predicted year of peak greenhouse gas emission. We based our projection on a forecast of climatic variables (extracted from WorldClim) from two global circulation models (CCSM4 and MIROC-ESM). Initially, we modeled current climatic suitability of habitat, individually for each of the 32 IWS, identifying those with a common spatial range of suitability. Thereafter, we modeled the suitability of all 32 species under the projected climate for 2050, incorporating each of the four Representative Concentration Pathways (2.6, 4.5, 6.0, and 8.5) in separate models, again examining the common spatial overlaps. The discrimination capacity and accuracy of the model were assessed for all 32 IWS individually, using the area under the curve and true skill statistic rate, with results averaging 0.87 and 0.75 respectively, indicating a high level of accuracy. Our final methodological step compared the extent of the overlaps and alterations under the current and future projected climates. Our results mainly predicted decrease on a global scale, in areas of habitat suitable for most IWS, under future climatic conditions, excluding European countries, northern Brazil, eastern US, and south-eastern Australia. The following should be considered when interpreting these results: there are many inherent assumptions and limitations in presence-only data of this type, as well as with the modeling techniques projecting climate conditions, and the envelopes themselves, such as scale and resolution mismatches, dispersal barriers, lack of documentation on potential disturbances, and unknown or unforeseen biotic interactions.
Read more: https://www.sciencedirect.com/science/article/abs/pii/S1470160X20303733?via%3Dihub
What does this mean for US agriculture?
Probably not a lot. My personal series of tests suggests weed killer works just as well in the tropics as it does in temperate climates. Local farmers also seem to manage. Ponds and waterways in the tropics are left to their own devices, or managed with an occasional bag of copper sulphate.
Worst case someone might have to order a few ship loads of tropical strength agricultural chemicals
There is a slight grain of truth to this, because of CO2 increase increasing growth of most but not all plants. Grasses and grains are mostly C4 plants, which have evolved to flourish in lower CO2 conditions, especially the mostly 180-280 PPMV of the Pleistocene (which we have yet to establish that we got out of). Their growth is not improved (at least not significantly) by increasing CO2 past 280 PPMV. (Although some of these probably have some improvement of drought tolerance from more CO2 due to less need of respiration of air.) Most other plants (including most weeds) are C3 plants, whose growth is significantly increased by increasing CO2 above Pleistocene levels. Their growth improvement from increase of CO2 level continues until CO2 reaches levels intentionally achieved in some greenhouses by means of CO2 generators, about 1000 PPMV.
“. . . a slight grain of truth . . .” Groan.
As a farmer who has been controlling weeds for over 60 years I would say that this study is about as worthless as a weed,
Weeds are plants in the wrong place ,such as rye grass in wheat crops or when the early settlers to New Zealand brought in gorse seed for hedges and now thousands of acres are covered in gorse and the cost to control it is a huge ongoing cost .
We have a huge problem with wilding pines in the South Island mountains .Pinus Contorta was planted to stabilize eroding gullies but they have spread over thousands of acres of productive sheep grazing land .
Our government in their eternal wisdom is allocating millions of dollars to eradicate these weed trees and at the same time have a plan to plant a billion trees on other land .
I have farm forestry blocks on my farm and forestry does have a place on steep gorse infected land .
When good farms are being brought up and planted in Pinus Radiata and we as tax payers are funding the investors carbon credits we as farmers object .
You can’t eat wood.
Proud to be farming feeding the world.
Graham
yeah they removed the feral…willows in sth aus riverbanks
and?
the next decent rains the banks caved in
and willows provided shade shelter for native critters
aussie version the broughton river willow is a woody weed grows in masses that make access to water near impossible and they burn so well too and theyre a magnet for the traveller caterpillars that denude everything in sight and cause grief with the fine hairs to birds etc silly enough to eat em
woods useless it stinks when burnt provides little heat and rots fast if used for anything else.
Heigh-Ho, Heigh-Ho, computer modelling we will go!
We did dig dig dig dig dig dig dig
In our Lab the whole day through
To dig dig dig dig dig dig dig dig
It’s what we like to do
It’s quite a trick
To get rich quick
If you dig dig dig
With a Graphic or a Hockey stick.
Must be true. I’ve been pulling weeds for years and they only seem to grow.
I was wondering what would happen in in July.
We’ve had Chinese crud and murder hornets.
The asteroids all missed.
So now we have the answer: giant mutant weeds from planet CO2.
Weeds are not a threat to agricultural productivity because modern farmers kill weeds with herbicides which food crops are resistant to. Unless we ban herbicides – which modern “do-gooders” try to.
Gwan, a farmer has it right. Investments should be in food and not taxing farmers to fund useless schemes.
I wonder if there are more weeds now than in 500BC….
What about the threatened insects? Maybe a weed diet will save them? Insects deserve diversity in diet….insect lives matter too.