If the biological success of invasive species is strengthened as a function of climate change, then critical measures must be taken. The first universally recognized step is, to halt and reverse the anthropogenic climate drivers (e.g. human sources of carbon dioxide and other greenhouse gases) responsible for climatic change. Because the globe is already showing signs of climatic uncertainty, a second goal is adaptation science. The two goals are connected and interdependent, but not necessarily so perceived at first glance.
From a USDA ARS technical abstract, IDENTIFYING AND MANIPULATING DETERMINANTS OF PHOTOSYNTHATE PRODUCTION AND PARTITIONING, researchable issues abound: “Elevated temperature treatments negated any enhancement in rice yield at elevated carbon dioxide, which suggests that identifying high temperature tolerant germplasm will be key to realizing yield benefits in the future.” [Rice Production in a Changing Climate: A Meta-analysis of Responses to Elevated Carbon Dioxide and Elevated Ozone Concentration] (Ainsworth, Elizabeth[lhz1] )
In other words, we need to understand the implications of climate change and we need to be working on adaptation now. Present projections are that we will need an increase of 20% in cereal production (i.e. wheat, rice and corn) to keep pace with population demand by 2020. A report, Food Gap Widening in Developing Countries- One in Four Children Worldwide Will be Malnourished in 2020. October 26, 1997 states that “Demand for cereals, especially for livestock feed, will increase rapidly. People in developing countries are expected to consume twice as much meat in 2020 as they did in 1993, causing demand for feed grain to double.”
How are we going to feed ourselves? How will we clean our water supply? Where will we find air suitable for human life? I may presume too much, but I think it highly unreasonable that we shall go back to a sustainable hunter gather society with the current and project human population numbers. This statement means that we shall need technological solutions with sustainability assumed as a fundamental prerequisite. We shall be in need of technology which recognizes that the earth for the foreseeable future is a closed system with finite resource limits.
The same set of climatic variables that are affecting cereal yields may also be affecting invasive species impacts on both traditional agriculture and current ecosystem management. A clarion call for action from natural area managers has focused on invasive species as a major threat to rare and endangered species. Invasive species have visibly out-competed native species and caused increased pressure on remaining populations. According NatureServe, “Invasive species are now regarded as the second-leading threat to imperiled species, behind only habitat destruction.”
Invasive species have also adversely affected agricultural production. A report from the Goodlatte Subcommittee states that “Invasive species represent a serious threat to the viability of American agriculture, forestry, and ecosystems. Not only can these harmful organisms cripple production agriculture, but society pays a great price for these harmful species including unemployment, damaged goods and equipment, power failures, food and water shortages, environmental degradation, increased rates and severity of natural disasters, and disease epidemics. The most obvious harm is found in agriculture. Farmers and ranchers are constantly battling alien pests, weeds, and diseases. Decreases in yield and quality of crops and livestock are easily attributed to invasive species. Producers fight stubborn weeds and pests year round – whether preparing for the planting season, during the growing season or harvest.”
The interconnection between climate dynamics, crop production and invasive species is easily seen. All plant species require carbon dioxide, water, light, and nutrients. If one of these resources changes abruptly, plant species will respond differentially. For example, too much water and the cactus dies; too little water and the wetland fern succumbs. Too much sun and the black cohosh is fried; too little sun and the pumpkin will not fruit. Add or decrease atmospheric carbon dioxide and plant species also respond differently, some will have the capacity to process the increase more efficiently; others will quietly be over come by the resulting competition. As carbon dioxide changes in the atmosphere, knowing which species will be more competitive has implications for not only agriculture (e.g. which rice varieties will be the best to grow?) but to invasive species as well (e.g. will kudzu be more of a threat in the future?)
In addition, increasing greenhouse gases such as carbon dioxide can result in changes in precipitation and temperature with subsequent results in species growth and adaptation. Here too, the same issues arise; how will we adapt agriculture to unprecedented changes in the environment that reflect temperature and precipitation extremes? How will these changes affect the success of invasive species and their subsequent impact on agriculture? Such complex issues underlie the need for more and immediate research while underscoring the complex connections between climate change, agriculture and invasive species.
In turn, invasive species concepts and challenges are connected to species shift. Species shift or species migration is movement of species from natural ranges in reaction to climate changes. For the layman this is not too hard a concept as humans do this on a regular basis. Snowbirds to Florida and skiers to the mountains are examples of in extremis of climate migration. In the long historical record of humanity, migrations for food, fuel, fiber, and feed are the movements of legend from the Germanic invasions of Rome to the emigration from Ireland during a time of famine. Species which once were unreliably hardy in Maryland now thrive, including but not limited to kudzu and fire ants.
The question then of ‘nativeness’ is no longer solely a question of where, but also of when. And more importantly, for the purposes of invasive species resource allocation, what are we trying to prevent, what are we trying to preserve exactly? If the threat is to endangered species then what are we to make of species shifts? If the rare and endangered are heading up and north, and the existing ecosystem is being stressed by climate change, what is the purpose of eradication efforts of invasives in ecosystem in flux? At the same time, we do know that preserving complex functioning ecosystems is important for the services provided and that invasive species pressure limits the ability of the system to provide these services, services such as clean water, clean air, and viable habitat.
It is once again not only natural areas which will feel the impact of species shift. “Rangelands will experience regional and local changes in temperature and precipitation. The CO2 has already increased to levels not experienced in the past million years and is projected to continue increasing far in the future. Plants have different sensitivities to temperature. Precipitation and CO2, and research suggest that plant shifts favoring some species over others is underway in rangelands. Research is needed to better understand such plant species shifts which have a tremendous impact on land’s utility. We need to use that knowledge to develop proactive management strategies that will help ranchers and public land managers adapt to climate change.” [From a presentation given to Maryland Senators Mikulski and Cardin’s staff, Dec 2008 http://www.nara-b.org/ )
According to a posting in ScienceDaily (Nov. 30, 2008), “…the distribution of many species is shifting because of climate change and changes in land use.” The feed-back loop of human activity on the environment and the environment’s impact on human activities becomes apparent in the previous quote. According to Dr. Lewis Ziska “one of the fundamental challenges we face in the 21st century is the unprecedented level of human-induced change.” [Controversies in Science Rising Atmospheric Carbon Dioxide and Plant Biology: The Overlooked Paradigm. DNA & Cell Biology Vol 27 Nov 2008]
For me this is a call for immediate and specific research looking for adaptive solutions.