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The Virtuous Weed - Nimal R Chandrasena


While the harm that weeds cause to humans remains the principal focus of Weed Science, we need to recognize that in many situations, weeds are beneficial to societies. Ralph Waldo Emerson once remarked, “A weed is a plant whose virtues have not yet been discovered.”


"The Virtuous Weed" book explores many of these virtues in weedy taxa, which are colonizing (pioneering) plants. Their utilization value to human societies is immense, as food, medicines and biofuels, as well as critical components of natural ecosystems and sustainable agro-ecosystems.


Weeds are also important in pollution remediation and supporting the livelihoods of people. Their flowery nectar and pollen are vital for pollinating insects and other animals. Weeds may also have a role in adapting to climatic change. Their genetic material can be unique sources of genes to improve crop varieties that could become more resilient to climatic change conditions. Colonizing plants might also be used to mitigate climate change, as new sources of energy, and as important components of ecological restoration after bushfires or as buffers for flooding.


Additional research needs to be done to fully elucidate the positive roles weeds could play in minimizing and adapting managed plant systems to an uncertain climate. However, there is a great wealth of evidence already available to indicate that weeds have many 'virtues' and should be respected for their variety of beneficial roles in Nature.


Weeds and Biodiversity


With or without humans colonizing species will always be present on earth and continue to play vital roles in stabilizing the earth's ecosystems damaged by the teeming humanity. Therefore, humans need to 'live with weeds' and utilize their colonizing power for beneficial uses.


If people well understand the valuable ecological roles and biodiversity values of colonizing species, it will influence the decision-makers and help them develop better policies towards colonizing taxa.


Agro-ecology helps us to appreciate the critical roles of colonizing taxa in Nature. Concepts such as 'beneficial weeds' and "middle-way path" to weed management allow us to re-think how we may engage in agriculture more sustainably. A change in thinking is required in Weed Science to recognize weeds, not as a production constraint in agriculture and a threat to farming, all the time.


As colonizing species, they are significant bio-resource assets.

Where the abundance of weeds, at particular times and locations, present problems for other essential and valued human endeavours (such as food production) or natural ecosystems, they need to be appropriately managed. People have done this for millennia. The tools and techniques to do so, to the extent required, are well developed within Weed Science – a formidable discipline.


An improved relationship with weeds will develop if they are understood as nothing but colonizing and pioneering taxa, which are adapted to respond to disturbances. Much like humans, they are just opportunistic species. Weeds are no more villainous than humans.


The farmland biodiversity discourses, especially in Europe and the U.K., have awakened research communities to explore a more tolerant attitude towards beneficial weeds. Weedy species contribute pollination benefits for bees and food for other insects. Various fauna use them as food and shelter resources. Colonizing species also play critical roles in mitigating soil erosion, water retention, nutrient cycling and replenishment, improving soil health.


Weedy congeners (relatives) also promote the evolutionary diversification and genes for hybridization with their crop relatives. Such positive contributions offset, at least partially, the losses to biodiversity that people allege weedy species cause. Biodiversity is too important for society to misunderstand it. Biodiversity is critically important for a healthy planet.


Human survival on Planet Earth depends on properly interacting with biodiversity. This includes appreciating the crucial roles colonizing species play.

‘Aliens’, ‘Natives’ and ‘Artificial Habitat’- Revisiting the Legacies of H.C. Watson and S.T. Dunn


Hewett Cottrell Watson, a British botanist and phyto-geographer, might rightfully be the first to apply the term ‘alien’ to denote ‘foreign’ species introduced to Britain, which successfully established at various locations in the isles with or without man’s help.


Botanists recognize Watson for his monumental work Cybele Britannica, written in four volumes over 12 years (1847-1859).


While applying the term ‘alien’, along with ‘natives’ (indigenous species), ‘denizens’ (long-term residents, introduced species, who might be considered ‘naturalized) and ‘colonists’ (species, colonizing agricultural land and habitat occupied by humans), Watson discussed in detail how difficult it is to assign ‘nativeness’ to any species.


Stephen Troyte Dunn, who wrote ‘Alien Flora of the British Isles’ in 1905, partly adopted H. C. Watson’s categorization of species. Both worked without much knowledge of the geological and fossil evidence of plants but agreed that all species, even ‘natives’, may have been immigrants sometime in the past.


All of Watson and Dunn’s ‘alien’ species have several things in common. They are all highly productive (fertile), pioneering or colonizing taxa, which can establish and thrive in disturbed environments (‘artificial habitat’, sensu S. T. Dunn), from which they perpetuate themselves.


Knowledge about the ‘foreign’ components of a country’s flora is ecologically important to understand how species adapt to new environments and influence others.


Both Watson and Dunn emphasized the remarkable ability of some introduced to spread, unassisted by man’s activities, while others, like ‘shadows of men’, appear to ‘follow the plough’.


The ‘colonization process’ of these highly successful plants gets them into trouble in the minds of some, who prefer to attribute other meanings, such as ‘invasions’ to these “foreign” species.


A dip into history shows that Watson and Dunn discussed introduced plants without disparaging them. Like humans, colonizing taxa are good at what they are genetically predisposed to do, i.e., adapt and survive even under stressful environments.


They are no more ‘alien’ than we are. They are also no more ‘invasive’ than we are. As one historian (Alfred Crosby) noted, these species may even help heal the wounds on the earth, torn apart by the real ‘invaders’ – those ‘wretched ingrates’ (humans).

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