Ecology and control of introduced plants (original) (raw)
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Weeds exist as a category of vegetation because of the human ability to select desirable traits from among various members of the plant kingdom. Just as some plants are valued for their uses or beauty, others are reviled for their apparent lack of these characteristics. Weeds are recognized worldwide as an important type of undesirable, economic pest, especially in agriculture. However, the value of any plant is unquestionably determined by the perceptions of its viewers. These perceptions also influence the human activities directed at this category of vegetation.
'Seeing Weeds with New Eyes' Part II-Some Historical Perspectives and 'Proto Weeds'
Weeds, 2020
“…What is a weed? A weed is a plant whose virtues have not yet been discovered…” Ralph Waldo Emerson (1863) Emerson, a renowned American philosopher, and poet, who led the transcendentalist movement of the mid-19th century in the USA, had an enlightened view of weeds. Those words, spoken in a famous speech, ‘Fortune of the Republic’, in December 1863, against the backdrop of the American Civil War (1860- 65), are often quoted in Weed Science textbooks. Their deeper meaning is: Weeds do have admirable virtues, and one would see them if one looked closely. As I said previously (Chandrasena, 2019), the incessant slandering of colonizing plants (weeds) by some people is a critical issue for Weed Science. It has inhibited the emerging generation of weed scientists from appreciating the utilitarian values and other redeeming qualities of weeds, as well as their ecological roles. It also prevents weed research from operating under a different paradigm and proving the worth of colonizing taxa, while controlling them to the extent necessary with sustainable approaches.
Living with Weeds - a new paradigm
Some people, particularly in developed countries, have strong negative attitudes towards weeds, and a tendency to label potentially useful plant resources as invasive ‘aliens’, which are to be controlled at any cost. This undesirable attitude ignores the considerable evidence of beneficial uses of weed species to many societies, over a long period of human history. The recent application of ‘species-focused’ weed risk assessments have contributed to the maligning of many plant taxa as ‘invaders’ in the public’s mind, undermining their worth as biological resources. Some of the methods used in the blitz against weeds, including the excessive use of herbicides, have resulted in undesirable consequences, such as herbicide resistance, and negative impacts on biodiversity in farming landscapes. Weeds maintain the biological diversity of farming landscapes, providing food and shelter for a variety of animals. Insects, which pollinate crops, extensively use weeds as a source of nectar, when crops are not in flower. Weeds also attract crop pests; and there is evidence that pest populations in some crops are much lower in ‘weedy fields’ than in ‘weed-free’ crops. As many of our primary crops have ‘weedy-relatives’, the genes present in weeds appear crucial for future evolution of crops, particularly to confer ‘hardiness’ (ability to tolerate variable environmental conditions). Some weed species contribute to aesthetic pleasure, as part of ‘wild nature’, while others provide culinary delights for humans, and are important as food sources for both vertebrate and invertebrate animals. Many weeds with medicinal values continue to be used either as traditional ‘herbal’ remedies, or extracted for secondary metabolites. The colonising strengths of several species are being used in the remediation of water and terrestrial environments to scavenge soil pollutants. Globally, there is considerable interest in using the large biomass produced by these species as raw materials for countless household products, including bricks, paper and furniture; and as future bio- fuels.Therefore, within the field of weed science, a fresh look at weeds is essential. Perhaps, a new and bold paradigm should be ‘co-existing’ or ‘living with weeds’, recognising their intrinsic worth as part of biodiversity, and the many possible uses as bio-resources. Key words: Beneficial effects of weeds, Colonising species, Utilization of weeds, Weeds as biological resources
The political ecology of weeds: a scalar approach to landscape transformations
The International Handbook of Political Ecology, 2015
Think globally, act locally' says the green maxim. Yet, when applied to plants labelled 'weeds' or 'invasive', this idea suggests a scalar mismatch. At the global level, invasive species are often listed alongside the biodiversity crisis and climate change as top environmental concerns with enormous economic ramifications. At the local level, any farmer or gardener will share the common human experience of intimate, sensory interactions with weeds -considering, touching, pulling, perhaps spraying. The global scale is dominated by lists, categories and costs; the local by praxis, need and emotion. The global is scientific and bureaucratic; the local is lived and pragmatic. There is a wealth of difference between and within these levels of scale -differences of power, perception and of geographical distribution; in short, a 'political ecology' of weeds that we review in this chapter. What interests us, as political ecologists of weeds, is when and how the quotidian movements of plants and processes of ecological and attendant social change -that is, their occurrence and spread across landscapes -become phenomena characterized as weeds or weed invasions and thereby objects of contention and control.
Led up the garden path? Weeds, conservation rhetoric, and environmental management
Australasian Journal of Environmental Management, 2017
At what scales does the concept of 'weed' really make sense? When and where does a garden plant become a weed, rather than just a garden plant? On a recent trip to the UK, one member of the project team (DK, a trained horticulturist and ecologist from Melbourne, Australia) was drawn to a sign beckoning passers-by to weed a meadow garden hanging on the wall (Fig. 1). At home, it is pretty obvious which plants 'belong' and which are weeds, both in gardens and in the bush. But in England it was not obvious at all. Which plants are weeds in this place where the rules are different from home? When and where does a plant become a weed? To take another international example, Monterey Pine (Pinus radiata) is a ubiquitous weed in the forests and woodlands of southeastern Australia, but is also listed on the IUCN Red List of Threatened Species as Endangered in its home range in central coastal California (Farjon, 2015). Weeds can be threatened species, and sometimes threatened species are weeds. It depends both on the biogeography of the place and the perspective of the weeder (Robbins, 2004).
… Journal of Agricultural …, 2007
Rapid population increase in southern Benin has changed the prevailing system of shifting cultivation into one of more permanent land use. New herbaceous weeds exacerbated rural poverty through crop failure, higher labour inputs, rising costs of production and reduced availability of suitable land. We investigated how different actors reacted to the emergence of weeds, in terms of the construction of knowledge, labour practices and technology development. Weeds have become an important cause of rural poverty. Farmers have actively engaged in technology development and new labour practices have emerged. Officials early on did report weed problems, especially where export crops were concerned. Researchers have not translated the new weed problem into a research priority until very recently, resulting in limited and inappropriate weed management technologies. The challenge of the research of which this study is part is to optimize weed management, by combining emergent indigenous weed management practices with scientific knowledge.
Australasian Journal of Environmental Management. , 2017
Draft (2016) of paper (2017) by Dave Kendal, Libby Robin, Anna Wilson, Cameron Muir, Lilian M. Pearce, Sharon Willoughby, Ian Lunt Final is locked behind a paywall. This is a paper I am often asked for. Sick of paywalls blocking practitioners from useful stuff At what scales does the concept of 'weed' really make sense? When and where does a garden plant become a weed, rather than just a garden plant?