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 University
Summary: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.
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