Biodiversity offsets and the challenge of achieving no net loss.

Businesses, governments, and financial institutions are increasingly adopting a policy of no net loss of biodiversity for development activities. The goal of no net loss is intended to help relieve tension between conservation and development by enabling economic gains to be achieved without concomitant biodiversity losses. biodiversity offsets represent a necessary component of a much broader mitigation strategy for achieving no net loss following prior application of avoidance, minimization, and remediation measures. However, doubts have been raised about the appropriate use of biodiversity offsets. We examined what no net loss means as a desirable conservation outcome and reviewed the conditions that determine whether, and under what circumstances, biodiversity offsets can help achieve such a goal. We propose a conceptual framework to substitute the often ad hoc approaches evident in many biodiversity offset initiatives. The relevance of biodiversity offsets to no net loss rests on 2 fundamental premises. First, offsets are rarely adequate for achieving no net loss of biodiversity alone. Second, some development effects may be too difficult or risky, or even impossible, to offset. To help to deliver no net loss through biodiversity offsets, biodiversity gains must be comparable to losses, be in addition to conservation gains that may have occurred in absence of the offset, and be lasting and protected from risk of failure. Adherence to these conditions requires consideration of the wider landscape context of development and offset activities, timing of offset delivery, measurement of biodiversity, accounting procedures and rule sets used to calculate biodiversity losses and gains and guide offset design, and approaches to managing risk. Adoption of this framework will strengthen the potential for offsets to provide an ecologically defensible mechanism that can help reconcile conservation and development. Balances de Biodiversidad y el Reto de No Obtener Pérdida Neta.

Net present biodiversity value and the design of biodiversity offsets.

There is an urgent need to develop sound theory and practice for biodiversity offsets to provide a better basis for offset multipliers, to improve accounting for time delays in offset repayments, and to develop a common framework for evaluating in-kind and out-of-kind offsets. Here, we apply concepts and measures from systematic conservation planning and financial accounting to provide a basis for determining equity across type (of biodiversity), space, and time. We introduce net present biodiversity value (NPBV) as a theoretical and practical measure for defining the offset required to achieve no-net-loss. For evaluating equity in type and space we use measures of biodiversity value from systematic conservation planning. Time discount rates are used to address risk of non-repayment, and loss of utility. We illustrate these concepts and measures with two examples of biodiversity impact-offset transactions. Considerable further work is required to understand the characteristics of these approaches.

An index of risk as a measure of biodiversity conservation achieved through land reform.

We measured the net progress of land reform in achieving a national policy goal for biodiversity conservation in the context of ongoing clearing of native vegetation and additions of land to a highly nonrepresentative (residual) reserve network, interior South Island, New Zealand. We used systematic conservation-planning approaches to develop a spatially explicit index of risk of biodiversity loss (RBL). The index incorporated information from national data sets that describe New Zealand's remaining indigenous land cover, legal protection, and land environments and modeled risk to biodiversity on the basis of stated assumptions about the effects of past habitat loss and legal protection. The index identified irreplaceable and vulnerable native habitats in lowland environments as the most at risk of biodiversity loss, and risk was correlated with the density of threatened plant records. To measure achievement, we used changes in the index that reflected gains made and opportunity costs incurred by legal protection and privatization. Application of the index to measure the difference made by land reform showed it had caused a net increase in the risk of biodiversity loss because most land vulnerable to habitat modification and rich in threatened plant species was privatized and land at least risk of biodiversity loss was protected. The application revealed that new high-elevation reserves did little to mitigate biodiversity decline, that privatization of low-elevation land further jeopardized the most vulnerable biodiversity in lowland native habitats, and that outcomes of land reform for biodiversity deteriorated over time. Further development of robust achievement measures is needed to encourage more accountable biodiversity conservation decisions.

Effect of history and exam in predicting electrodiagnostic outcome among patients with suspected lumbosacral radiculopathy.

OBJECTIVE: To determine the extent to which the history and physical examination predict the outcome of the electrodiagnostic (EDX) evaluation in patients with suspected lumbosacral radiculopathy. DESIGN: Data for 170 subjects referred for low-back and lower limb symptoms were prospectively collected at five EDX laboratories. The sensitivity, specificity, positive and negative predictive values, and odds ratios were determined for symptoms and neurologic signs. RESULTS: Symptoms were not significantly associated with an EDX study or a lumbosacral radiculopathy. The physical examination was better at predicting that an EDX study would be abnormal in general than it was at predicting a lumbosacral radiculopathy in particular. Of those subjects with normal physical examinations, 15%-18% still had abnormal EDX findings. CONCLUSIONS: In a population of patients referred for an EDX study, the history and physical examination alone cannot reliably predict electrodiagnostic outcome.

Predicting electrodiagnostic outcome in patients with upper limb symptoms: are the history and physical examination helpful?

OBJECTIVE: To determine the effectiveness of medical history and physical examination in predicting electrodiagnostic outcome in patients with suspected cervical radiculopathy. METHODS: Data on 183 subjects prospectively collected at five different electrodiagnostic laboratories were analyzed (96 cervical radiculopathies, 45 normal studies, and 42 abnormal electrodiagnostic findings other than radiculopathy). The sensitivity, specificity, positive predictive value, negative predictive value, and odds ratios were determined for symptoms and neurologic signs. RESULTS: Symptoms of numbness, weakness, and tingling were associated with twice the probability of having abnormal electrodiagnostic study results in general, yet were not helpful in identifying a cervical radiculopathy. All single and combined physical examination components had poor sensitivities, with the exception of weakness, but much higher specificities. Patients with either weakness or reduced reflexes on physical examination were up to five times more likely to have abnormal electrodiagnostic findings. In subjects with any abnormal neurologic sign, the sensitivity improved to 84%, the positive predictive value was 79%, but the specificity was low (44%). Of those subjects with normal physical examination results, almost one half had an abnormal electrodiagnostic study result (negative predictive value 52%). CONCLUSIONS: In a population of patients with suspected cervical radiculopathy, medical history and physical examination are helpful yet not sufficient to predict the electrodiagnostic outcome.

Symptom duration and spontaneous activity in lumbosacral radiculopathy.

OBJECTIVES: A long-held notion in the electrodiagnostic literature is that paraspinal muscles tend to show spontaneous activity (fibrillations and positive sharp waves) on needle electromyography, early on in a lumbosacral radiculopathy, and that more distal muscles become abnormal later in the disease process. The purpose of this study was to determine whether paraspinal muscle and other major proximal and distal muscle spontaneous activity is related to a lumbosacral radiculopathy symptom duration. METHODS: A multicenter, prospective study that collected standard information on history, physical examination, and electrodiagnostic findings in patients with electrodiagnostically confirmed lumbosacral radiculopathies was undertaken. RESULTS: Multivariate probit analyses of 96 patients identified with a lumbosacral radiculopathy showed no evidence of correlation between spontaneous activity in the paraspinal muscles and symptom duration. Symptom duration was also nonsignificant in nine of the remaining ten lower limb muscles analyzed. CONCLUSION: These findings emphasize the limitations of using symptom duration when interpreting electrodiagnostic findings in lumbosacral radiculopathy.

Identifying lumbosacral radiculopathies: an optimal electromyographic screen.

OBJECTIVE: The objective of this study was to determine prospectively the optimal electromyographic screening examination of the lower limb that ensures identification of those lumbosacral radiculopathies that can be electrodiagnostically confirmed, yet minimizes the number of muscles studied. DESIGN: A prospective multicenter study was conducted from May 1996 to September 1997. Patients with suspected lumbosacral radiculopathy referred to participating electrodiagnostic laboratories were recruited and examined by needle electromyography using a standard set of muscles. Patients with electrodiagnostically confirmed lumbosacral radiculopathies were selected for analysis. Various muscle screens were tested against this group of patients with radiculopathies to determine the frequency with which each screen identified the patient with radiculopathy. RESULTS: There were 102 patients identified. When paraspinal muscles were one of the screening muscles, four-muscle screens identified 88-97% of the radiculopathies, five-muscle screens identified 94-98%, and six-muscle screens 98-100%. When paraspinal muscles were not part of the screen, identification rates were lower for all screens, and eight distal muscles were necessary to identify about 90% of the radiculopathies. CONCLUSIONS: Six-muscle screens with paraspinal muscles yielded consistently high identification rates. Studying additional muscles produced no improvements in identification.

Identification of cervical radiculopathies: optimizing the electromyographic screen.

OBJECTIVE: To determine the optimal electromyography screening examination of the upper limb that ensures detection of those cervical radiculopathies, which can be electrodiagnostically confirmed, yet minimizes the number of muscles studied. DESIGN: A prospective multicenter study was conducted from May 1996 to September 1997 at five institutions. Patients who were referred to participating electrodiagnostic laboratories with suspected cervical radiculopathy were recruited. A standard set of muscles were examined by needle electromyography. Patients with electrodiagnostically confirmed cervical radiculopathies, based on electromyography findings, were selected for analysis. Muscle screens were tested against this group to determine whether the screen identified the patients with radiculopathy. RESULTS: There were 101 patients with cervical radiculopathies representing all cervical root levels. When paraspinal muscles were one of the screening muscles, five muscle screens identified 90% to 98% of radiculopathies, six muscle screens identified 94% to 99%, and seven muscle screens identified 96% to 100%. When paraspinal muscles were not part of the screen, eight distal limb muscles recognized 92% to 95% of radiculopathies. CONCLUSION: This study demonstrated that six muscle screens including paraspinal muscles yielded consistently high identification rates. Studying additional muscles led to marginal increases in identification.