A new study published in Science demonstrates how the rise of modern agriculture has transformed a native North American plant, the common waterhemp, into a problematic agricultural weed.
An international team led by researchers at the University of British Columbia (UBC) compared 187 waterhemp samples from modern farms and nearby wetlands to more than 100 historical samples dating back to 1820 that were stored in museums across North America.
The study of the plant's genetic makeup over the last two centuries allowed the researchers to watch evolution in action across changing environments, much like the sequencing of ancient human and neanderthal remains has resolved key mysteries about human history.
How intensive agriculture turned a wild plant into a pervasive weed
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According to first author Dr. Julia Kreiner, a postdoctoral researcher in UBC's Department of Botany, the genetic variants that help the plant thrive in modern agricultural settings have risen to high frequencies remarkably quickly since agricultural intensification in the 1960s, as per ScienceDaily.
The researchers discovered hundreds of genes that contribute to the weed's success on farms, with mutations in genes associated with drought tolerance, rapid growth, and herbicide resistance.
Dr. Kreiner stated, "The types of changes we're imposing in agricultural environments are so strong that they have consequences in neighboring habitats that we'd normally think were natural."
The findings could help conservation efforts to protect natural areas in agricultural landscapes. Reducing gene flow out of agricultural sites and protecting more isolated natural populations could help limit farms' evolutionary influence.
Waterhemp is a plant native to North America that was not always a problem.
According to Dr. Kreiner, modern farms impose a strong filter that determines which plant species and mutations can survive over time. Herbicides emerged as one of the most powerful agricultural filters for determining which plants survive and which die when the plant's genes were sequenced.
Since 1960, waterhemp with any of the seven herbicide-resistant mutations has produced an average of 1.2 times as many surviving offspring per year as plants without the mutations.
Herbicide-resistant mutations have also been discovered in natural habitats, though at a lower frequency, raising concerns about the costs of these adaptations for plant life in non-agricultural settings.
Being resistant can be costly to a plant in the absence of herbicide applications, so the changes occurring on farms are affecting the fitness of the plant in the wild, according to Dr. Kreiner.
Agricultural practices have also altered the distribution of specific genetic variants across the landscape. A weedy southwestern variety has spread its genes eastward across North America over the last 60 years, spreading its genes into local populations as a result of its competitive advantage in agricultural contexts.
Related
Disadvantages of Intensive Farming
Intensive farming is highly criticized and thought to be cruel to animals. The use of various chemicals, growth hormones, and overcrowding in a small space usually result in poor living conditions and hygiene for the livestock, as per Conserve Energy Future.
Keeping livestock beyond their carrying capacity causes pollution and poor hygiene, which leads to infections and other diseases.
As previously stated, intensive farming involves the use of a variety of agrochemicals, such as chemical pesticides, fertilizers, herbicides, insecticides, and acaricides.
When these chemicals are used, they not only kill the pests, weeds, and parasites that they are designed to kill, but they also contaminate food.
Environmental studies and reports show that intensive farming has a wide range of negative effects on the environment.
Massive deforestation and soil erosion have resulted from the removal of trees, slush and burn techniques, and the clearing of forest areas to make way for agriculture.
As a result, natural habitats and wild animals have suffered greatly as a result of the destructive practices that have persistently contributed to habitat loss.
Chemical fertilizers and herbicides pollute water soils, wildlife habitats, and bodies of water such as oceans, rivers, and lakes.
The main cause of eutrophication in most of the world's water bodies, such as oceans, lakes, and rivers, is fertilizer nutrients.
The vegetables and fruits are sourced from areas that practice intensive farming and are contaminated with invisible pesticides.
The problem is that pesticides cannot be easily washed away, and because fruits and vegetables appear clean after a simple wash, humans consume the chemical pesticides indirectly.
Pesticides have an impact on human health, posing risks such as physical deformity, skin allergies, and congenital diseases.
ADHD in children, for example, has been linked to pesticide consumption in agricultural food products.
