Learning Word Representations with Hierarchical Sparse Coding

We propose a new method for learning word representations using hierarchical regularization in sparse coding inspired by the linguistic study of word meanings. We show an efficient learning algorithm based on stochastic proximal methods that is significantly faster than previous approaches, making it possible to perform hierarchical sparse coding on a corpus of billions of word tokens. Experiments on various benchmark tasks---word similarity ranking, analogies, sentence completion, and sentiment analysis---demonstrate that the method outperforms or is competitive with state-of-the-art methods. Our word representations are available at \url{http://www.ark.cs.cmu.edu/dyogatam/wordvecs/}

Elephants and the Ivory Trade Ban: Summary of Research Results

economics of elephant conservation, economics of ivory trade,trade bans

Identifying the important factors in simulation models with many factors

Simulation models may have many parameters and input variables (together called factors), while only a few factors are really important (parsimony principle). For such models this paper presents an effective and efficient screening technique to identify and estimate those important factors. The technique extends the classical binary search technique to situations with more than a single important factor. The technique uses a low-order polynomial approximation to the input/output behavior of the simulation model. This approximation may account for interactions among factors. The technique is demonstrated by applying it to a complicated ecological simulation that models the increase of temperatures worldwide.Simulation Models;econometrics

An Economic Analysis of Mountain Pine Beetle Impacts in a Global Context

The economic effects of the mountain pine beetle outbreak in British Columbia are simulated using a multi-region spatial price equilibrium model coupled with a stochastic dynamic updating procedure. The simulation captures expected changes in the B.C. timber supply, growth of plantation forests in the southern hemisphere and an escalating Russian log export tax. The results indicate lumber and log prices will rise in B.C., offsetting some of the economic loss to timber producers. However, on net producers in the B.C. forest industry will experience a decrease in economic surplus.Mountain pine beetle; spatial price equilibirum; trade modeling

Regional Log Market Integration in New Zealand

In this paper the integration of log prices across four regions in New Zealand was assessed. A time series of prices for six Radiata Pine (Pinus radiata D. Don) log grades in each of the regions were tested for co-integration using Johansen’s method and Engle-Granger pair wise tests. Prices for export grades display significant integration across regions and generally follow the law of one price. However, markets for domestic grades tend to be regionally segregated. These results are most likely due to the high costs of transporting logs between regions. Future modelling will need to incorporate such transportation costs in order to adequately characterise log markets in the country.log market; co-integration; law of one price

Biological Carbon Sinks: Transaction Costs and Governance

Activities that remove CO2 from the atmosphere and store it in forest and agricultural ecosystems can generate CO2-offset credits that can thus substitute for CO2 emissions reduction. Are biological CO2-uptake activities competitive with CO2 offsets from reduced fossil fuel use? In this paper, it is argued that transaction costs impose a formidable obstacle to direct substitution of carbon uptake offsets for emissions reduction in trading schemes, and that separate caps should be set for emissions reduction and sink-related activities. While a tax/subsidy scheme is preferred to emissions trading for incorporating biologically-generated CO2 offsets, contracts that focus on the activity and not the amount of carbon sequestered are most likely to lead to the lowest transaction costs.carbon sequestration; transaction costs; climate change

Modeling the mobility of living organisms in heterogeneous landscapes: Does memory improve foraging success?

Thanks to recent technological advances, it is now possible to track with an unprecedented precision and for long periods of time the movement patterns of many living organisms in their habitat. The increasing amount of data available on single trajectories offers the possibility of understanding how animals move and of testing basic movement models. Random walks have long represented the main description for micro-organisms and have also been useful to understand the foraging behaviour of large animals. Nevertheless, most vertebrates, in particular humans and other primates, rely on sophisticated cognitive tools such as spatial maps, episodic memory and travel cost discounting. These properties call for other modeling approaches of mobility patterns. We propose a foraging framework where a learning mobile agent uses a combination of memory-based and random steps. We investigate how advantageous it is to use memory for exploiting resources in heterogeneous and changing environments. An adequate balance of determinism and random exploration is found to maximize the foraging efficiency and to generate trajectories with an intricate spatio-temporal order. Based on this approach, we propose some tools for analysing the non-random nature of mobility patterns in general.Comment: 14 pages, 4 figures, improved discussio

Conservation Payments under Risk: A Stochastic Dominance Approach

Conservation payments can be used to preserve forest and agroforest systems. To explain landowners’ land-use decisions and determine appropriate conservation payments, it is necessary to focus on revenue risk. Marginal conditional stochastic dominance rules are used to derive conditions for determining the conservation payments required to guarantee that the environmentally-preferred land use dominates. An empirical application to shaded-coffee protection in the biologically important Chocó region of West-Ecuador shows that conservation payments required for preserving shaded-coffee areas are much higher than those calculated under risk-neutral assumptions. Further, the extant distribution of land has strong impacts on the required payments.agroforest systems, conservation payments, land allocation, portfolio diversification, risk, stochastic dominance

What Makes Mountain Pine Beetle a Tricky Pest? Difficult Decisions when Facing Beetle Attack in a Mixed Species Forest

The pine forest of British Columbia is undergoing its largest recorded pest epidemic. The damage caused by native mountain pine beetle creates difficulties for the public owner of the resource, which is interested in protecting future timber supply while salvaging dead and dying pine. This paper addresses two problems that have often been over-looked: the variability and timing of beetle attack, and the variability of pine inventory in each stand. Management controls are limited to the annual rate of harvest and timber product outputs are based on shelf life – the length of time infested timber can still be used to produce lumber. Using mathematical programming to schedule harvest, we introduce a novel objective function based on the maximization of the net returns of the timber portfolio at the end of the 20 year time horizon under harvest and product flow constraints implemented by the public landowner to insure stability in the forest sector, and especially a stable supply of feedstock (bushchips) for bio-energy production, while recovering value from stands that would otherwise become uneconomical to harvest. The optimal short-run response is to increase harvests over the baseline harvest without beetle. The use of future net returns as the optimization objective ensures that harvest during the 20 year time horizon occurs in stands that would otherwise be economically unharvestable and also the harvest is generally above 70% pine in aggregate. Net returns do not exceed those of the baseline harvest without beetle, regardless of the scenario, as the harvest of low value bushchips must be subsidized by the harvest of timber that can be converted into lumber. Shelflife provides significant changes in NPV as more timber can be converted to lumber if shelflife is longer. The government has a difficult fiscal management problem. Employing an evenflow of total harvest can yield higher net gains but at the risk of relying more heavily on the harvest of damaged timber and reduced future harvests of quality timber for dimensional lumber. This strategy would produce a “feast” of short term revenue followed by a “famine” when bushchip harvest is subsidized by the harvest of better quality timber. Alternatively, managing the individual forest products could yield some minimum government revenues but this strategy could also lead to the need to deplete reserves that could be reserved for future timber supply. Regardless of the strategy, to optimize for future timber supply potential means that a large percentage (25% in this study) of the damaged pine should only be harvested in the future and will not be of a quality to produce lumber