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

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

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

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,

ECONOMIC PROSPECTS FOR SMALL-SCALE FUEL ALCOHOL PRODUCTION

Small-scale alcohol plants will have difficulty in supplying fuel that is competitive in cost with petroleum-based fuels. This is based upon economic findings form interdisciplinary research with a pilot fuel alcohol plant. Results of economic-engineering cost analyses and of fuel and feed byproduct returns analyses are shown. Fuel and feed transportation costs are also considered in determining the economic feasibility prospects for small-scale plants producing hydrous ethanol from grain.Resource /Energy Economics and Policy,

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

Shocks, cooling and the origin of star formation rates in spiral galaxies

Understanding star formation is problematic as it originates in the large scale dynamics of a galaxy but occurs on the small scale of an individual star forming event. This paper presents the first numerical simulations to resolve the star formation process on sub-parsec scales, whilst also following the dynamics of the interstellar medium (ISM) on galactic scales. In these models, the warm low density ISM gas flows into the spiral arms where orbit crowding produces the shock formation of dense clouds, held together temporarily by their external pressure. Cooling allows the gas to be compressed to sufficiently high densities that local regions collapse under their own gravity and form stars. The star formation rates follow a Schmidt-Kennicutt \Sigma_{SFR} ~ \Sigma_{gas}^{1.4} type relation with the local surface density of gas while following a linear relation with the cold and dense gas. Cooling is the primary driver of star formation and the star formation rates as it determines the amount of cold gas available for gravitational collapse. The star formation rates found in the simulations are offset to higher values relative to the extragalactic values, implying a constant reduction, such as from feedback or magnetic fields, is likely to be required. Intriguingly, it appears that a spiral or other convergent shock and the accompanying thermal instability can explain how star formation is triggered, generate the physical conditions of molecular clouds and explain why star formation rates are tightly correlated to the gas properties of galaxies.Comment: 13 pages, 12 figures. MNRAS in pres