What Are Ecosystem Services?

This paper advocates consistently defined units of account to measure the contributions of nature to human welfare. We argue that such units have to date not been defined by environmental accounting advocates and that the term “ecosystem services” is too ad hoc to be of practical use in welfare accounting. We propose a definition, rooted in economic principles, of ecosystem service units. A goal of these units is comparability with the definition of conventional goods and services found in GDP and the other national accounts. We illustrate our definition of ecological units of account with concrete examples. We also argue that these same units of account provide an architecture for environmental performance measurement by governments, conservancies, and environmental markets.Environmental accounting, ecosystem services, index theory, nonmarket valuation

The Architecture and Measurement of an Ecosystem Services Index

This paper describes the construction of an ecological services index (ESI). An ESI is meant to summarize and track over time the magnitude of beneficial services arising from the natural environment. A central task of this paper is to define rigorously ecosystem services so that services can be counted in an economically and ecologically defensible manner—a requirement if ecological contributions to welfare are to be incorporated into the national accounts. This paper advocates a particular economic structure and relates it to index theory and makes concrete recommendations for the measurement of such an index.ecosystem services, Green GDP, index numbers, ecological economics

Limits of Nematoscelis megalops in the northwestern Atlantic in relation to Gulf Stream cold core rings. II, Physiological and biochemical effects of expatriation

Originally published in the Journal of Marine Research, v. 36, 1, 1978, pp. 143-159Nematoscelis megalops, a cold water euphausiid commonly found in Northwestern Atlantic Slope Water, is frequently transported in the cores of Gulf Stream cyclonic rings into the Sargasso Sea. The inner core made of cold Slope Water gradually assumes physical and biological characteristics of the surrounding Sargasso Sea. These changes gradually lead to a localized extinction of this species in the core of the ring. Samples of N. megalops taken from the same ring at 6 and 9 months after its formation show a weakened physiological and biochemical condition. Deterioration of ring individuals is evidenced by an increase in body water content and a reduction in total body lipid, carbon, respiration rates, and nitrogen relative to Slope Water individuals. By 6 months it appears that ring N. megalops must supplement food intake by metabolizing some of their body protein and by 9 months they appear to use lipids as well. A shipboard starvation experiment involving 40 Slope Water individuals showed that physiological and biochemical states similar to those found in individuals from the 9 months old ring could be duplicated in 4 days of complete starvation.Prepared for the Office of Naval Research under Contracts N00014-66-C-0241; NR 083-004 and N00014-?4-C-0262; NR 083-004 and for the National Science Foundation under Grant DES ?4-02?83 A01

Host-Switching Does not Circumvent the Ni-based Defence of the Ni hyperaccumulator \u3ci\u3eStreptanthus polygaloides\u3c/i\u3e (Brassicaceae)

Elevated tissue concentrations of metals have been shown to defend metal-hyperaccumulating plants against both herbivores and pathogens. Tolerance of metal-based defences presents a challenge to herbivores, because heavy metals cannot be degraded or metabolized. One strategy that herbivores can employ to counter high-metal defences is dietary dilution, or host switching. Highly mobile herbivores are most likely to use this strategy, but less mobile lepidopteran larvae can also Improve their performance on toxic hosts if early instar development occurs on more favourable hosts. We examined the effects of host switching on growth and survival of a generalist folivore. Specifically, we tested the hypothesis that early larval development on non-toxic hosts could improve larval performance of the beet armyworm, Spodoptera exigua, an high-Ni Streptanthus polygaloides, a Ni hyperaccumulator. Initial larval performance (weight gain) was lowest for insects switched to high-N! hosts. Decreased initial larval performance was also noted for insects switched from lettuce to low-Ni S. polygaloides, but these larvae recovered quickly. Original host identity (lettuce or low-Ni S. polygaloides) did not affect subsequent larval performance. By day 8 of the feeding trials, all larvae switched to high-Ni hosts had died. We conclude that polyphagous Spodoptera larvae are unable to counter NI-based defences via host switching

Anhydrous ammonia application losses using single-disc and knife fertilizer injector

Anhydrous ammonia (NH3) is injected below the soil surface during application to limit loss to the atmosphere. Application at a shallower depth may reduce tractor power or allow greater speed, which could increase field capacity if NH3 losses are held to acceptable levels. Losses of NH3 during, and for 1 h after, field application were measured from a typical knife injector treatment operated at a 15-cm (6-in.) depth and 8-km/h (5-mph) travel speed and from a single-disc injector operated at shallower depths [5 and 10 cm (2 and 4 in.)] and a range of travel speeds [8, 12, and 16 km/h (5, 7.5, and 10 mph)]. NH3 losses during application as measured with a hood over the single-disc injector were 3% to 7% in clay loam, silty clay loam, and loam soils and 21% to 52% in a coarser-textured fine sandy loam soil. Applying with a knife injector at deeper depth resulted in losses of 1% to 2% across all soil types. NH3 losses measured during an hour after application with stationary collection over the injection trench were 1% or less for all treatments. Losses during application were 5 to 55 times greater than during the first hour after application

Field Evaluation of Anhydrous Ammonia Manifold Performance

Experiments conducted between August 1999 and April 2002 evaluated anhydrous ammonia manifold distribution during field application at 84- and 168-kg N/ha (75- and 150-lb N/acre) application rates. Multiple manifolds including the conventional (Continental NH3 Model 3497, Dallas, Tex.), Vertical-Dam (Continental NH3 Dallas, Tex.), RotaflowTM(H.I. Fraser Pty Ltd, Sydney, Australia), Equa-flowTM(PGI International, Houston, Tex.), FD-1200 prototype (CDS John Blue Co., Huntsville, Ala.), and the Impellicone prototype manifold were tested. Temperature and pressure data were collected along the flow path.Results showed high distribution variation by the conventional manifold at both application rates, with average coefficient of variation (CV) values in excess of 16%. At the 84-kg N/ha (75-lb N/acre) rate, all other manifolds tested had significantly lower application variation (. = 0.05). At the 168-kg N/ha (150-lb N/acre) rate, the conventional manifold grouped statistically with the Vertical-Dam with a corn ring and the FD-1200 prototype, producing CV values between 9.5% and 16.2%. All other manifolds had significantly lower application variation. The Impellicone, Rotaflow., and Equa-flow., manifolds performed with the lowest measured variation at both rates, yielding best performance at the 168-kg N/ha (150-lb N/acre) rate with CV in the 6% range.Analysis of recorded temperature and pressure data indicate that NH3 flowing through the system very closely follows the saturation line and acts as a saturated mixture. Predictions of NH3 quality based on calculations of an ideal adiabatic mixture are supported by this result. Investigation for correlation between CV, air temperature, and percent of volume in the vapor phase of NH3 resulted in only a visual trend that may suggest a reduction in CV with lower percent of volume in the vapor phase.Results suggest that replacement of a conventional manifold with a Vertical-Dam manifold or any of the other manifolds tested could reduce application variation between 7.0% and 16.5% at 84 kg N/ha (75 lb N/acre) and 1.0% and 10.2% at 168 kg N/ha (150 lb N/acre). This change could reduce application rate by eliminating the need for over-application to compensate for variations

Fertilizer Application: NH, Opener Losses and Uniformity Issues

Anhydrous ammonia (NH3) is injected below the soil surface during application to limit loss to the atmosphere. Application at a shallower depth may reduce tractor horsepower or allow greater speed which could increase field capacity of equipment if NH3 losses are held to acceptable levels. Losses of NH3 during, and for one hour after, field application were measured from a typical knife injector treatment operated at a 15-cm (6-in.) depth and 8 km/h (5 mi/h) travel speed and from a single-disc injector operated at shallower depths (5 and 10 cm (2 and 4 in.)) and a range of travel speeds (8, 12, and 16 km/h (5, 7.5, and 10 mi/h)). NH3 losses during application as measured with a hood over the single-disc injector were 3 to 7% in clay loam, silty clay loam, and loam soils and 21 to 52% in a coarser-textured fine sandy loam soil. Applying with a knife injector at deeper depth resulted in losses of 1 to 2% across all soil types. NH3 losses measured during an hour after application with stationary collection over the injection trench were 1% or less for all treatments. Losses during application were 5 to 55 times greater than during the first hour after application

Field Application Uniformity of Impellicone and Pulse-Width-Modulated Anhydrous Ammonia Manifolds

With the consistently increasing cost and widespread use of anhydrous ammonia (NH3), producers are looking for ways to reduce variability in applicator equipment. One way to improve uniformity in NH3 applicators is the use of a better distribution manifold. Impellicone and pulse-width-modulated (PWM) manifolds are newer design alternatives to a Vertical-Dam manifold. Uniformity measurements during field application were made comparing Vertical-Dam manifolds with several Impellicone manifold designs and also a pulse-width-modulated (PWM) valve design as these manifolds were refined for commercial production. Application rates ranged from 23.7 to 224 kg N/ha (21.2 to 200 lb N/acre) depending on experiment with many applications near 84 kg N/ha (75 lb N/acre; “low” rate) and 168 kg N/ha (150 lb N/acre; “high” rate) during Impellicone tests. Modified Impellicone and PWM manifolds both had better uniformity at a 99% confidence level (as measured by lower coefficients of variation (CVs)) than did Vertical-Dam manifolds tested during the same field conditions. Modified Impellicone manifolds had average coefficients of variation (CVs) 9 and 6 percentage points lower, than the Vertical-Dam manifold at the low rate and high application rates, respectively. The PWM manifold CV was 3 percentage points lower than the Vertical-Dam at application rates of 95 kg N/ha (85 lb N/acre), but 6 and 13 percentage points lower than the Vertical-Dam manifold at application rates of 179 and 22 kg N/ha (160 and 20 lb N/acre, respectively)