Santa Fe Institute

About: Santa Fe Institute is a nonprofit organization based out in Santa Fe, New Mexico, United States. It is known for research contribution in the topics: Population & Context (language use). The organization has 558 authors who have published 4558 publications receiving 396015 citations. The organization is also known as: SFI.

Biological scaling: does the exception prove the rule?

Abstract: Arising from: P. B. Reich, M. G. Tjoelker, J.-L. Machado & J. Oleksyn , 457–461 (2006)10.1038/nature04282 ; Reich et al. reply , Hedin reply Reich et al.1 report that the whole-plant respiration rate, R, in seedlings scales linearly with plant mass, M, so that when θ ≈ 1, in which cR is the scaling normalization and θ is the scaling exponent. They also state that because nitrogen concentration (N) is correlated with cR, variation in N is a better predictor of R than M would be. Reich et al. and Hedin2 incorrectly claim that these “universal” findings question the central tenet of metabolic scaling theory, which they interpret as predicting θ = ¾, irrespective of the size of the plant. Here we show that these conclusions misrepresent metabolic scaling theory and that their results are actually consistent with this theory.

Hedge Funds, Systemic Risk, and the Financial Crisis of 2007-2008: Written Testimony for the House Oversight Committee Hearing on Hedge Funds

Abstract: This document is the written testimony submitted to the House Oversight Committee for its hearing on hedge funds and the financial crisis, held November 13, 2008, and is not a formal academic research paper, but is intended for a broader audience of policymakers and regulators. Academic readers may be alarmed by the lack of comprehensive citations and literature review, the imprecise and qualitative nature of certain arguments, and the abundance of illustrative examples, analogies, and metaphors. Accordingly, such readers are hereby forewarned - this paper is not research, but is instead a summary of the policy implications that I have drawn from my interpretation of that research. I begin with a proposal to measure systemic risk, and argue that this is the natural starting point for regulatory reform since it is impossible to manage something that cannot be measured. Then I review the relation between systemic risk and hedge funds, and show that early warning signs of the current crisis did exist in the hedge-fund industry as far back as 2004. However, I argue that financial crises may be an unavoidable aspect of human behavior, and the best we can do is to acknowledge this tendency and be properly prepared. This behavioral pattern, as well as traditional economic motives for regulation - public goods, externalities, and incomplete markets - are relevant for systemic risk or its converse, systemic safety, and I suggest applying these concepts to the functions of the financial system to yield a rational process for regulatory reform. Also, I propose the formation of a new investigative office patterned after the National Transportation Safety Board to provide the kind of information aggregation and transparency that is called for in the previous sections. Another aspect of transparency involves fair-value accounting, and I review some of the recent arguments for its suspension and propose developing a new branch of accounting focusing exclusively on risk. I conclude with a discussion of the role of financial technology and education in the current crisis, and argue that more finance training is needed, not less.

Social Insect Colonies as Complex Adaptive Systems

Abstract: Social insect societies are complex adaptive systems that self-organize within a set of constraints. Although it is important to acknowledge that global order in social insects can arise as a result of internal interactions among insects, it is equally important to include external factors and constraints in the picture, especially as the colony and its environment may influence each other through interactions among internal and external factors. The scope of this remark goes beyond social insects and applies to a wide range of biological systems, including ecosystems.

Structure of the species-energy relationship

Abstract: The relationship between energy availability and species richness (the species-energy relationship) is one of the best documented macroecological phenomena. However, the structure of species distribution along the gradient, the proximate driver of the relationship, is poorly known. Here, using data on the distribution of birds in southern Africa, for which species richness increases linearly with energy availability, we provide an explicit determination of this structure. We show that most species exhibit increasing occupancy towards more productive regions (occurring in more grid cells within a productivity class). However, average reporting rates per species within occupied grid cells, a correlate of local density, do not show a similar increase. The mean range of used energy levels and the mean geographical range size of species in southern Africa decreases along the energy gradient, as most species are present at high productivity levels but only some can extend their ranges towards lower levels. Species turnover among grid cells consequently decreases towards high energy levels. In summary, these patterns support the hypothesis that higher productivity leads to more species by increasing the probability of occurrence of resources that enable the persistence of viable populations, without necessarily affecting local population densities.