Reconciling approaches to climate change adaptation for Colombian agriculture

The projected impact of climate change on agro-ecological systems is considered widespread and significant, particularly across the global tropics. As in many other countries, adaptation to climate change is likely to be an important challenge for Colombian agricultural systems. In a recent study, a national-level assessment of the likely future impacts of climate change on agriculture was performed (Ramirez-Villegas et al. Clim Chang 115:611–628, 2012, RV2012). The study diagnosed key challenges directly affecting major crops and regions within the Colombian agricultural system and suggested a number of actions thought to facilitate adaptation, while refraining from proposing specific strategies at local scales. Further insights on the study were published by Feola (2013) (F2013), who stressed the need for transformative adaptation processes to reduce vulnerability particularly of resource-limited farmers, and the benefits of a predominantly stakeholder-led approach to adaptation. We clarify that the recommendations outlined in RV2012 were not intended as a recipe for multi-scale adaptation, but rather a set of actions that are required to diagnose and develop adaptation actions particularly at governmental levels in coordination with national and international adaptation initiatives. Such adaptation actions ought to be, ideally, a product of inclusive sub-sectorial assessments, which can take different forms. We argue that Colombian agriculture as a whole would benefit from a better outlining of adaptation needs across temporal scales in sub-sectorial assessments that take into account both RV2012 and F2013 orientations to adaptation. We conclude with two case studies of research on climate change impacts and adaptation developed in Colombia that serve as examples of realistic, productive sectorial and sub-national assessments.     

The Oxford Principles

Scientific momentum is increasing behind efforts to develop geoengineering options, but it is widely acknowledged that the challenges of geoengineering are as much political and social as they are technical. Legislators are looking for guidance on the governance of geoengineering research and possible deployment. The Oxford Principles are five high-level principles for geoengineering governance. This article explains their intended function and the core societal values which they attempt to capture. Finally, it proposes a framework for their implementation in a flexible governance architecture through the formulation of technology-specific research protocols.     

Variations in dissolved CO2 and CH4 in a first‐order stream and catchment: an investigation of soil–stream linkages

Spatial and seasonal variations in CO₂ and CH₄ concentrations in streamwater and adjacent soils were studied at three sites on Brocky Burn, a headwater stream draining a peatland catchment in upland Britain. Concentrations of both gases in the soil atmosphere were significantly higher in peat and riparian soils than in mineral soils. Peat and riparian soil CO₂ concentrations varied seasonally, showing a positive correlation with air and soil temperature. Streamwater CO₂ concentrations at the upper sampling site, which mostly drained deep peats, varied from 2·8 to 9·8 mg l^?1 (2·5 to 11·9 times atmospheric saturation) and decreased markedly downstream. Temperature‐related seasonal variations in peat and riparian soil CO₂ were reflected in the stream at the upper site, where 77% of biweekly variation was explained by an autoregressive model based on: (i) a negative log‐linear relationship with stream flow; (ii) a positive linear relationship with soil CO₂ concentrations in the shallow riparian wells; and (iii) a negative linear relationship with soil CO₂ concentrations in the shallow peat wells, with a significant 2‐week lag term. These relationships changed markedly downstream, with an apparent decrease in the soil–stream linkage and a switch to a positive relationship between stream flow and stream CO₂. Streamwater CH₄ concentrations also declined sharply downstream, but were much lower (<0·01 to 0·12 mg l^?1) than those of CO₂ and showed no seasonal variation, nor any relationship with soil atmospheric CH₄ concentrations. However, stream CH₄ was significantly correlated with stream flow at the upper site, which explained 57% of biweekly variations in dissolved concentrations. We conclude that stream CO₂ can be a useful integrative measure of whole catchment respiration, but only at sites where the soil–stream linkage is strong. Copyright © 2004 John Wiley & Sons, Ltd.     

Probing the wind–wind collision in γ2 Velorum with high-resolution Chandra X-ray spectroscopy: evidence for sudden radiative braking and non-equilibrium ionization

We present a new analysis of an archived Chandra HETGS X-ray spectrum of the WR+O colliding wind binary γ² Velorum. The spectrum is dominated by emission lines from astrophysically abundant elements: Ne, Mg, Si, S and Fe. From a combination of broad-band spectral analysis and an analysis of line flux ratios we infer a wide range of temperatures in the X-ray-emitting plasma (∼4–40 MK). As in the previously published analysis, we find the X-ray emission lines are essentially unshifted, with a mean FWHM of  1240 ± 30 km s⁻¹  . Calculations of line profiles based on hydrodynamical simulations of the wind–wind collision predict lines that are blueshifted by a few hundred  km s⁻¹  . The lack of any observed shift in the lines may be evidence of a large shock-cone opening half-angle (>85°), and we suggest this may be evidence of sudden radiative braking. From the R and G ratios measured from He-like forbidden-intercombination-resonance triplets we find evidence that the Mg  xi emission originates from hotter gas closer to the O star than the Si  xiii emission, which suggests that non-equilibrium ionization may be present.     

Intrinsic variational equations for conservative dynamical systems withN degrees of freedom

For a conservative dynamical system withn deg. of freedom we show that the equations of variation along an orbit may be written with respect to an orthonormal moving frame (a generalized Frenet frame) in which the tangential variation is given by a quadrature and the normal andn-2 binormal variations are solutions ofn-1 coupled second order equations of the form of Hill's equation.