Harbour porpoises (Phocoena phocoena) and minke whales (Balaenoptera acutorostrata) observed during land-based surveys in The Minch, north-west Scotland

Peer reviewedPublisher PD

On the reliability of composite analysis:an example of wet summers in North China

The validity of composite analysis is seldom discussed despite the fact that it can yield conflicting results. Our study confirms its validity by adding a reliability analysis to the classical composite analysis. Based on the signals extracted from composite analysis, 10 of the 14 wet summers in North China (1951–2020) can be “predicted” retrospectively. This study suggested the cyclonic anomaly over Mongolia at 500- and 850-hPa is closely associated with wet summers in North China. Interestingly, we found the most profound effects come from the Southern Hemisphere, with high confidence levels and large magnitude of the composite anomalies. These composite results are further cross-validated. We show that, based on the signals extracted from composite analysis, previously unseen wet summers in North China can be predicted with the mean absolute percentage error (MAPE) around 6%.</p

Captive breeding cannot sustain migratory Asian houbara Chlamydotis macqueenii without hunting controls

To evaluate the potential contribution of captive breeding to the conservation of exploited migratory Asian houbara Chlamydotis macqueenii, we estimated release numbers required to stabilise a population in a hunting concession (14,300 km2), under scenarios of local licensed hunting and flyway-scale protection. We developed a population model, initially 2350 adult females, re-sampling parameters measured through fieldwork and satellite telemetry, over 1000 iterations. With current flyway-scale unregulated harvest, and without any licensed hunting in the concession, populations declined at 9.4% year-1 (95% CI: –18.9 to 0% year-1); in this scenario a precautionary approach (85% probability λ≥ 1.0) to population stabilisation required releasing 3100 captive-bred females year-1 (131% x initial wild numbers). A precautionary approach to sustainable hunting of 100 females year-1 required releasing 3600 females year-1 (153% initial wild numbers); but if interventions reduced flyway-scale hunting/trapping mortality by 60% or 80%, sustaining this quota required releasing 900 or 400 females year-1, 38% and 17% of initial wild numbers, respectively. Parameter uncertainty increased precautionary numbers for release, but even with reduced precaution (50% probability λ≥ 1.0), sustainable hunting of 100 females year-1 required annual releases of 2200 females (94% wild) without other measures, but 300 (13%) or no (0%) females under scenarios of a 60% or 80% reduction in flyway-scale hunting/trapping. Captive breeding cannot alone sustain migrant populations of wild C. macqueenii because it risks replacement and domestication. Trade and exploitation must be restricted to avoid either extinction or domestication. For exploited populations, supplementation by captive breeding should be used with caution

Rainfall validates MODIS-derived NDVI as an index of spatio-temporal variation in green biomass across non-montane semi-arid and arid Central Asia

As satellite-derived normalized difference vegetation index (NDVI) is related to vegetation biomass, it may provide a proxy for habitat quality across extensive species ranges where ground-truth data are scarce. However, NDVI may have limited accuracy in sparsely-vegetated arid and semi-arid environments due to signal contamination by substrate reflectance. To validate NDVI as a vegetation proxy in the low-altitude deserts of Central Asia, we examine its response to precipitation across the migratory corridor of Asian Houbara. NDVI increases with precipitation, both spatially (adj. R2 = 0.58, p < 0.001) and temporally (mean adj. R2 across n=244, 1 degree cells = 0.44; GLMM across cells p < 0.001). More vegetated regions show a stronger temporal response of vegetation biomass for a given precipitation increment (slope of NDVI to precipitation in per cell temporal models increases with inter-annual mean NDVI; adj. R2 = 0.38, p < 0.001), reinforcing the conclusion that NDVI provides a proxy for vegetation abundance. The strong signature of rainfall shows MODIS NDVI offers a potentially powerful proxy for spatial and temporal variation in arid and semi-arid vegetation at a resolution of 1 degree and 1 year over the houbara's breeding and wintering range, and probably also at finer spatial resolutions

Detecting regional variability in sources and sinks of carbon dioxide: a synthesis

The current paper reviews the experimental setup of the CarboEurope Experimental Strategy (CERES) campaigns with the aim of providing an overview of the instrumentation used, the data-set and associated modelling. It then assesses progress in the field of regional observation and modelling of carbon fluxes, bringing the papers of this special issue into a somewhat broader context of analysis. &lt;br&gt;&lt;br&gt; Instrumental progress has been obtained in the field of remotely monitoring from tall towers and the experimental planning. Flux measurements from aircraft are now capable, within some constraints, to provide regular regional observations of fluxes of CO&lt;sub&gt;2&lt;/sub&gt;, latent and sensible heat. &lt;br&gt;&lt;br&gt; Considerable effort still needs to be put into calibrating the surface schemes of models, as they have direct impact on the input of energy, moisture and carbon fluxes in the boundary layer. Overall, the mesoscale models appear to be capable of simulating the large scale dynamics of the region, but in the fine detail, like the precise horizontal and vertical CO&lt;sub&gt;2&lt;/sub&gt; field differences between the models still exist. These errors translate directly into transport uncertainty, when the forward simulations are used in inverse mode. Quantification of this uncertainty, including that of inadequate boundary layer height modelling, still remains a major challenge for state of the art mesoscale models. Progress in inverse models has been slow, but has shown that it is possible to estimate some of the errors involved, and that using the combination of observations. Overall, the capability to produce regional, high-resolution estimates of carbon exchange, exist in potential, but the routine application will require considerable effort, both in the experimental as in the modelling domain

Regional carbon fluxes and the effect of topography on the variability of atmospheric CO2.

Using a mesoscale atmospheric circulation model, it is shown that relatively modest topography height differences of ∼500 m over 200 km near Zotino (60°N, 89°E) in central Siberia may generate horizontal gradients in CO<inf>2</inf> concentration in the order of 30 ppm. In a case study for 15 and 16 July 1996, when Lloyd et al. (2001) conducted a convective boundary layer budget experiment in the area, we show that advection of these gradients disturbs the relation between diurnal concentration changes in the boundary layer and the surface fluxes. This demonstrates that mesoscale atmospheric heterogeneity may have severe impact on the applicability of methods to derive the regional-scale fluxes from CO<inf>2</inf> concentrations measurements, such as the convective boundary layer budget method or inverse modeling. It is shown that similar mesoscale gradients are likely to occur at many long-term observation stations and tall towers. We use the modeled concentration fields to quantify the horizontal and vertical variability of carbon dioxide in the atmosphere. In future observation campaigns, mesoscale processes may be best accounted for by measuring horizontal variability over a few hundred kilometers and by attempting to quantify the representation errors as a function of mesoscale conditions. Copyright 2007 by the American Geophysical Union

Consistent nest-site selection across habitats increases fitness in Asian Houbara

Nest-site choice profoundly influences reproductive success and the survival of incubating adults. Asian Houbara (Chlamydotis macqueenii) nest in subtly contrasting habitats where the main cause of nest failure is predation. We examined nest-site selection across three semi-arid shrub habitats that differed in vegetation structure and hypothesized that increased concealment would reduce nest predation. We quantified vegetation structure at 210 nests and 194 random control sites at two scales, the ‘nest area’ (50 m radius, considering mean ‘shrub height’ and mean ‘shrub frequency’) and ‘nest scrape’ (2 m radius,  considering a ‘concealment index’). Variance ratio tests showed variance in both shrub height and concealment index were lower at nests than at random sites, indicating non-random selection. Analysis of the probability of nest occurrence for nest area indicated consistent selection of intermediate shrub heights (shrub height + shrub height2) in the Astragalus, Salsola arbuscula and S. rigida shrub assemblages (29.5–31.5 cm), although this was not supported statistically in S. rigida as the vegetation available was already similar to the optimal nest structure. Nest survival analysis, controlling for date, showed that shrub height (but not its quadratic term) in the nest area reduced nest predation rate. Females likely traded off nesting in even taller shrubs that may confer greater nest success against the ability to see approaching danger and thus to reduce the risk of being depredated themselves (head height during vigilance when incubating is ~30cm), as we have no records of females being depredated on the nest. At the nest scrape, females strongly selected better concealed locations, although the concealment index did not affect nest success. We suggest that concealing the scrape among shrubs may have other roles, such as thermoregulation

Toekomstbeeld broeikasgasbalans van het Nederlandse landschap

De mondiale emissies van CO2 zijn de afgelopen jaren substantieel gestegen. Een afbuiging van deze trend lijkt noodzakelijk, wil de concentratie in de atmosfeer niet te hoog oplopen. De internationale gemeenschap probeert die te realiseren door stevige reductiedoelstellingen vast te stellen voor de komende tien tot dertig jaar. De inspanningen zijn gericht op terugdringen van emissies, compensatie van de uitstoot door afvang en opslag van CO2 en de omschakeling naar een duurzame energievoorziening

Longer growing seasons do not increase net carbon uptake in Northeastern Siberian tundra

With global warming, snowmelt is occurring earlier and growing seasons are becoming longer around the Arctic. It has been suggested that this would lead to more uptake of carbon due to a lengthening of the period in which plants photosynthesize. To investigate this suggestion, 8 consecutive years of eddy covariance measurements at a northeastern Siberian graminoid tundra site were investigated for patterns in net ecosystem exchange, gross primary production (GPP) and ecosystem respiration (Reco). While GPP showed no clear increase with longer growing seasons, it was significantly increased in warmer summers. Due to these warmer temperatures however, the increase in uptake was mostly offset by an increase in Reco. Therefore, overall variability in net carbon uptake was low, and no relationship with growing season length was found. Furthermore, the highest net uptake of carbon occurred with the shortest and the coldest growing season. Low uptake of carbon mostly occurred with longer or warmer growing seasons. We thus conclude that the net carbon uptake of this ecosystem is more likely to decrease rather than to increase under a warmer climate. These results contradict previous research that has showed more net carbon uptake with longer growing seasons. We hypothesize that this difference is due to site-specific differences, such as climate type and soil, and that changes in the carbon cycle with longer growing seasons will not be uniform around the Arcti