Working Lands Agri-environmental Policy Options and Issues for the Next United States Farm Bill

U.S. farm legislation is due to be updated in 2007, to become effective with the 2008 crop year. Major questions surround the role of environmental or conservation provisions in the new Federal farm bill. In this paper, I first present some background on the evolution of U.S. ‘agri-environmental policies’—policies encompassing conservation of agriculture’s natural resources and agriculture’s impact on the environment. I follow that with a brief discussion of the concept of ‘multifunctionality’ in agriculture, a concept that increasingly is driving discussions of agri-environmental policy options in Europe and the U.S. The subsequent section of the paper contains discussion of four broad alternative approaches to agri-environmental policy in the next farm bill. Then, there are sections on each of three specific agri-environmental programs and sets of policies: the Environmental Quality Incentives Program, the Conservation Security Program, and policies to support organic agriculture. I conclude the paper with my observations on prospects for fundamental reforms related to agri-environmental policies in the next farm bill.farm legislation, agri-environmental policy, conservation, farm bill

TOWARD MORE EFFECTIVE INVOLVEMENT OF AGRICULTURAL ECONOMISTS IN MULTIDISCIPLINARY RESEARCH AND EXTENSION PROGRAMS

Multidisciplinary research and extension involving agricultural economics and sister agricultural disciplines entail several tensions arising out of differences in perspective and methodology. Recognition of these differences is essential to the achievement of effective and productive working relationships in farming systems and other multidisciplinary research and extension endeavors. Problems and means of addressing differences are covered in this article.Teaching/Communication/Extension/Profession,

The Myth of the Molecular Ring

We investigate the structure of the Milky Way by determining how features in a spatial map correspond to CO features in a velocity map. We examine structures including logarithmic spiral arms, a ring and a bar. We explore the available parameter space, including the pitch angle of the spiral arms, radius of a ring, and rotation curve. We show that surprisingly, a spiral arm provides a better fit to the observed molecular ring than a true ring feature. This is because both a spiral arm, and the observed feature known as the molecular ring, are curved in velocity longitude space. We find that much of the CO emission in the velocity longitude map can be fitted by a nearly symmetric 2 armed spiral pattern. One of the arms corresponds to the molecular ring, whilst the opposite arm naturally reproduces the Perseus arm. Multiple arms also contribute to further emission in the vicinity of the molecular ring and match other observed spiral arms. Whether the Galactic structure consists primarily of two, or several spiral arms, the presence of 2 symmetric logarithmic spirals, which begin in the vicinity of the ends of the bar, suggest a spiral density wave associated with the bar.Comment: 7 pages, 2 figures, accepted by MNRA

The Exciting Lives of Giant Molecular Clouds

We present a detailed study of the evolution of GMCs in a galactic disc simulation. We follow individual GMCs (defined in our simulations by a total column density criterion), including their level of star formation, from their formation to dispersal. We find the evolution of GMCs is highly complex. GMCs often form from a combination of smaller clouds and ambient ISM, and similarly disperse by splitting into a number of smaller clouds and ambient ISM. However some clouds emerge as the result of the disruption of a more massive GMC, rather than from the assembly of smaller clouds. Likewise in some cases, clouds accrete onto more massive clouds rather than disperse. Because of the difficulty of determining a precursor or successor of a given GMC, determining GMC histories and lifetimes is highly non-trivial. Using a definition relating to the continuous evolution of a cloud, we obtain lifetimes typically of 4-25 Myr for >10^5 M$_{\odot}$ GMCs, over which time the star formation efficiency is about 1 %. We also relate the lifetime of GMCs to their crossing time. We find that the crossing time is a reasonable measure of the actual lifetime of the cloud, although there is considerable scatter. The scatter is found to be unavoidable because of the complex and varied shapes and dynamics of the clouds. We study cloud dispersal in detail and find both stellar feedback and shear contribute to cloud disruption. We also demonstrate that GMCs do not behave as ridge clouds, rather massive spiral arm GMCs evolve into smaller clouds in inter-arm spurs.Comment: 15 pages, 16 figures, accepted for publication in MNRA

The evolution of Giant Molecular Filaments

In recent years there has been a growing interest in studying giant molecular filaments (GMFs), which are extremely elongated (> 100pc in length) giant molecular clouds (GMCs). They are often seen as inter-arm features in external spiral galaxies, but have been tentatively associated with spiral arms when viewed in the Milky Way. In this paper, we study the time evolution of GMFs in a high-resolution section of a spiral galaxy simulation, and their link with spiral arm GMCs and star formation, over a period of 11Myrs. The GMFs generally survive the inter-arm passage, although they are subject to a number of processes (e.g. star formation, stellar feedback and differential rotation) which can break the giant filamentary structure into smaller sections. The GMFs are not gravitationally bound clouds as a whole, but are, to some extent, confined by external pressure. Once they reach the spiral arms, the GMFs tend to evolve into more substructured spiral arm GMCs, suggesting that GMFs may be precursors to arm GMCs. Here, they become incorporated into the more complex and almost continuum molecular medium that makes up the gaseous spiral arm. Instead of retaining a clear filamentary shape, their shapes are distorted both by their climb up the spiral potential and their interaction with the gas within the spiral arm. The GMFs do tend to become aligned with the spiral arms just before they enter them (when they reach the minimum of the spiral potential), which could account for the observations of GMFs in the Milky Way.Comment: 15 pages, 11 figures, MNRAS accepte

'Organic' and 'Conventional' Grain and Soybean Prices in the Northern Great Plains and Upper Midwest: 1995 through 2003

As part of the sustainable agriculture research program in the Economics Department at South Dakota State University (SDSU), ‘organic’ and ‘conventional’ crop prices have been compared for nearly a decade. This pamphlet serves as an update of price comparisons through 2003 and a final conclusion of the price series comparison, which we will no longer continue. The pamphlet also contains brief reference to another source of organic price data (see the appendix). The information in this pamphlet should be of use to farmers and others considering management changes and investments related to organic agriculture, as well as to policy makers.organic foods, food prices, soybean, grain

Clumpy and fractal shocks, and the generation of a velocity dispersion in molecular clouds

We present an alternative explanation for the nature of turbulence in molecular clouds. Often associated with classical models of turbulence, we instead interpret the observed gas dynamics as random motions, induced when clumpy gas is subject to a shock. From simulations of shocks, we show that a supersonic velocity dispersion occurs in the shocked gas provided the initial distribution of gas is sufficiently non-uniform. We investigate the velocity size-scale relation $\sigma \propto r^{\alpha}$ for simulations of clumpy and fractal gas, and show that clumpy shocks can produce realistic velocity size-scale relations with mean $\alpha \thicksim 0.5$. For a fractal distribution, with a fractal dimension of 2.2 similar to what is observed in the ISM, we find $\sigma \propto r^{0.4}$. The form of the velocity size-scale relation can be understood as due to mass loading, i.e. the post-shock velocity of the gas is determined by the amount of mass encountered as the gas enters the shock. We support this hypothesis with analytical calculations of the velocity dispersion relation for different initial distributions. A prediction of this model is that the line-of sight velocity dispersion should depend on the angle at which the shocked gas is viewed.Comment: 11 pages, 17 figures, accepted for publication in MNRA

Spiral arm triggering of star formation

We present numerical simulations of the passage of clumpy gas through a galactic spiral shock, the subsequent formation of giant molecular clouds (GMCs) and the triggering of star formation. The spiral shock forms dense clouds while dissipating kinetic energy, producing regions that are locally gravitationally bound and collapse to form stars. In addition to triggering the star formation process, the clumpy gas passing through the shock naturally generates the observed velocity dispersion size relation of molecular clouds. In this scenario, the internal motions of GMCs need not be turbulent in nature. The coupling of the clouds' internal kinematics to their externally triggered formation removes the need for the clouds to be self-gravitating. Globally unbound molecular clouds provides a simple explanation of the low efficiency of star formation. While dense regions in the shock become bound and collapse to form stars, the majority of the gas disperses as it leaves the spiral arm.Comment: 6 pages, 4 figures: IAU 237, Triggering of star formation in turbulent molecular clouds, eds B. Elmegreen and J. Palou

Giant Molecular clouds: what are they made from, and how do they get there?

We analyse the results of four simulations of isolated galaxies: two with a rigid spiral potential of fixed pattern speed, but with different degrees of star-formation induced feedback, one with an axisymmetric galactic potential and one with a `live' self-gravitating stellar component. Since we use a Lagrangian method we are able to select gas that lies within giant molecular clouds (GMCs) at a particular timeframe, and to then study the properties of this gas at earlier and later times. We find that gas which forms GMCs is not typical of the interstellar medium at least 50 Myr before the clouds form and reaches mean densities within an order of magnitude of mean cloud densities by around 10 Myr before. The gas in GMCs takes at least 50 Myr to return to typical ISM gas after dispersal by stellar feedback, and in some cases the gas is never fully recycled. We also present a study of the two-dimensional, vertically-averaged velocity fields within the ISM. We show that the velocity fields corresponding to the shortest timescales (that is, those timescales closest to the immediate formation and dissipation of the clouds) can be readily understood in terms of the various cloud formation and dissipation mechanisms. Properties of the flow patterns can be used to distinguish the processes which drive converging flows (e.g.\ spiral shocks, supernovae) and thus molecular cloud formation, and we note that such properties may be detectable with future observations of nearby galaxies.Comment: 13 pages, 8 figures, accepted for publication in MNRA