The first objective of this project is to provide basic geographic information on the potential distribution of damaging and invasive weed species in US agricultural systems in a changing climate. To our knowledge, this has not been previously attempted. The second phase of this project will assess how to best make use of this information. For example, when is it useful to target climatically-favored weed species for control?
impact statement issue
The potential impact of evolving atmospheric chemistry and climate change have been extensively studied for many facets of natural and managed ecosystems. Within agriculture, several efforts have investigated the impact of elevated CO2 on comparative weed and crop physiology, while others have quantified the role of environmental factors like temperature and drought on the competitive balance of different crop-weed associations. Indirect impacts of global change may also prove important, with some studies reporting that herbicide efficacy will be reduced with rising atmospheric CO2. Less explored aspects of global change is its likely impact on the geographic distribution of agricultural weed species. Climate factors are the principal determinants of vegetation distribution at the regional to global scales. Hence, transformations in the geographic range of damaging and invasive agricultural weeds are highly probable outcomes from global climate change. The implications of these transformations could be severe. Changes to weed community composition may degrade the efficacy of existing weed control strategies and also the yield and economic costs to producers from uncontrolled weeds. Moreover, important ecosystem services provided by weeds may be compromised if community composition evolves with climate change.
impact statement response
An initial analysis for this project was completed in the winter of 2007-2008 with results presented at the Northeast Weed Science Society annual meeting in Philadelphia. We are proposing through the Weed Science Society of America an initiative to improve the survey data of weeds in North America agricultural systems that would be useful for refining projections of climate impacts on invasive weed distribution.
impact statement summary
By the end of the century, climate change projections under business-as-usual emissions scenarios suggest a warming of 3 – 5 degrees C accompanied by an increased occurrence of very dry and very wet periods in North America. If these forecasts are realized, agricultural systems are likely to experience an increased vulnerability to invasive weed species. To anticipate these risks and to devise management strategies for proactively addressing them, it is essential to understand the environmental conditions that make specific weed species abundant, competitive, and therefore damaging to crop production. Maize forms the most extensive agroecosystem in the United States with approximately 93 million acres planted in 2007. This project couples state-based climate change projections with weed survey data to evaluate, through space-for-time substitution techniques, what changes can be expected to damaging weed communities in US maize systems. I found that the geographic distribution of troublesome species is likely to be radically transformed by climate change. In some states, potential nearer-term changes are commensurate to those possible by the end of the century. Moreover, weed communities in the Northeast may experience more significant transformation than other U.S. regions. Emerging climate niches in the Southern U.S. suggests new vulnerabilities to exotics species that are not currently found in North America.\n
