Harvest Levels Research Articles

Forecasting wildfire-induced declines in potential forest harvest levels across Québec

Wildfires are increasing in importance in many regions of the Canadian boreal forest and are an ongoing risk for forest management activities. We simulated the effects of fires on long-term harvest levels on the 59 forest management units of the province of Québec, Canada, for the 2020–2100 period. Different climate change pathways (stable, RCP 4.5 or 8.5) and salvage logging rates (20% or 70% of mature burned stands) were simulated. Changes in forest flammability due to climate change, species migration, and forest management were also considered. Under stable climatic conditions, the decline in potential harvest levels due to fire, based on 50 simulations per scenario, ranged between 3% and 33% (mean = 11%) when high salvage logging rates were simulated, compared to 6%–45% (mean = 20%) for low salvage rates. Climate change caused increases in burn rates between −3% and 39% for RCP 4.5 and between 33% and 69% for RCP 8.5 at the end of the 21st century, depending on fire zones. However, the effects of these modified burn rates on harvest levels did not differ substantially from those of baseline burn rates, probably because the projected burn rates were highest during the later part of the simulations (2070–2100), when their impacts on harvest level calculations were limited. This study indicates that potential harvest levels calculated without considering wildfires are likely to be non-sustainable.

Examining techno-economic interactions among fish species: A case of small-scale demersal fishery

Using the multi-product dual revenue function framework, this paper examines the nature and extent of technical and economic interactions among five demersal species of Al-Batinah demersal fishery, Oman during the 2010–2016 period. The parameters of the system of output supply functions are estimated using Zellner's seemingly unrelated regressions (SUR) technique. The likelihood ratio test in relation to the structure of the multi-output production technology rejects the null-hypothesis of input-output separability and non-jointness in inputs. These results suggest that the underlying production technology is non-separable between the outputs and the quasi-fixed input, and the harvesting level of one species is likely to have spill-over economic effects on the harvesting levels of others. The own-price elasticities of output supply are found to be positive, inelastic, and statistically significant in four out of five cases suggesting that, other things being equal, fishers' supply decisions are influenced by the prevailing market prices of outputs. The estimated values of the cross-price elasticity of supply are negative, inelastic and statistically significant at the 5% level for eight output pairs. The calculated values of the Morishima elasticity of substitution (MES) indicate the presence of substitutability between ten output pairs. The cross-price elasticity estimates are in the range of −0.001 (between Emperor and Catfish) to −0.275 (between Seabream and Grouper) which is lower (in absolute value) than that of the MES estimates. The magnitudes of the cross-price elasticity and the MES estimates indicate the extent of spill-over effects of one species on the other and signal the extent of species targeting by fishers. A statistically significant spatial, seasonal, and inter-annual variability is observed in all species cases. Finally, the implications of the findings are discussed from the perspective of developing effective management approaches, achieving sustainability of fisheries resources and improving fishers' socio-economic conditions stipulated in the Five-Year development plans for the sector.

Biomechanical knee energy harvester: Design optimization and testing

Biomechanical energy harvesters are designed to generate electrical energy from human locomotion (e.g., walking) with minimal or no additional effort by the users. These harvesters aim to carry out the work of the muscles during phases in locomotion where the muscles are acting as brakes. Currently, many harvesters focus on the knee joint during late swing, which is only one of three phases available during the gait cycle. For the device to be successful, there is a need to consider design components such as the motor/generator and the gear ratio. These components influence the amount of electrical energy that could be harvested, metabolic power during harvesting, and more. These various components make it challenging to achieve the optimal design. This paper presents a design of a knee harvester with a direct drive that enables harvesting both in flexion and extension using optimization. Subsequently, two knee devices were built and tested using five different harvesting levels. Results show that the 30% level was the best, harvesting approximately 5 W of electricity and redacting 8 W of metabolic energy compared to walking with the device as a dead weight. Evaluation of the models used in the optimization showed a good match to the system model but less for the metabolic power model. These results could pave the way for an energy harvester that could utilize more of the negative joint power during the gait cycle while reducing metabolic effort.

Effects of Small-Scale Mining Activities on Fisheries and Livelihoods in the Birim River in Atiwa District, Eastern Region of Ghana

The socioeconomic importance of small-scale mining in Ghana is of great interest to the country. It provides employment, supports the livelihood of poor rural areas, and also contributes to national income. Despite all these importance, it has a great influence on the surroundings, with surface and groundwater bodies being the most affected. The study was conducted to determine the effects of small-scale mining activities on fisheries and livelihoods along the Birim River in Atiwa District of Ghana, and also, to ascertain the nature of mining in the catchment and the current status of fisheries in the river. Data were collected with a help of open and closed ended questionnaire and fishers were sampled using purposive sampling method. Findings revealed that fishing activity was vibrant before 2010, but declined afterward. Respondents indicated that the number of fishers who went fishing daily before 2010 decreased drastically after 2010. Also, before 2010, most of the fishers (62%) used fishing nets compared to that after 2010. About 74% of respondents revealed that they could harvest at most 5 crates of fish a day before 2010, while about 38.6% of respondents indicated they could harvest 5 crates after 2010; thus 25 kg per day before 2010. It was revealed that 34% of respondents indicated they could make above $10 daily before 2010 as against 2% making $10 per day after 2010. About 90% of the respondents attributed their levels of harvest and average income per day to the effects of mining, with the reason being that miners wash their products in the river (52%), thus polluting the waterbody. Mining in water locally and commonly known as “changfan” was the main type of mining in the study area. From the findings, it is concluded that small-scale mining has detrimental effects on aquatic ecology and has resulted in the creation of deep pits which destroy gears, increasing the costs of gear repairs, fishing effort, and pollutes water (physical and chemical factors). Hence, it is recommended that there should be a ban on all small-scale mining in and around water bodies as this has detrimental effects on water quality and reduce fishing in the area.
 Keywords: Pollution; small-scale mining; Birim River; Changfan; Atiwa; Ghana

Risk perception and political leaning explain the preferences of non-industrial private landowners for alternative climate change mitigation strategies in Finnish forests

Understanding landowners’ willingness to act on climate change is important for effective climate policy. This study investigates the determinants of Finnish non-industrial private forest owners’ preferences for alternative climate change mitigation strategies related to forests and wood use. The study tests hypotheses concerning the role of risk perception and political leaning for the support of seven alternative strategies with varying degree of disruption to the current logic of commercial forestry in Finland, which further aligns with the temporal delay in the impact of climate change mitigation strategies that landowners are willing to accept. Based on 887 survey responses from three regions, the study finds that forest owners generally support all but one of the seven strategies: reduced harvest. Results from ordinal logistic regression models further indicate that along with socio-demographic determinants, higher perceived risk and left-wing leaning with a university degree explain support for more disruptive strategies with more immediate mitigation impact (increased conservation, reduced harvest), while lower perceived risk and right-wing leaning without a university degree tend to associate with support for the less disruptive strategies (intensified management, increased harvest), both of which arguably sideline the urgency of climate action. In the highly politicized matter of harvest levels in Finland, the study also finds that right-wing leaning may negate the effect of higher education, which otherwise predicts greater support for more disruptive strategies. Implications for policy at the climate-forest nexus are derived.

Modeling and Analysis of the Influence of Fear on a Harvested Food Web System

The food web is a crucial conceptual tool for understanding the dynamics of energy transfer in an ecosystem, as well as the feeding relationships among species within a community. It also reveals species interactions and community structure. As a result, an ecological food web system with two predators competing for prey while experiencing fear was developed and studied. The properties of the solution of the system were determined, and all potential equilibrium points were identified. The dynamic behavior in their immediate surroundings was examined both locally and globally. The system’s persistence demands were calculated, and all conceivable forms of local bifurcations were investigated. With the aid of MATLAB, a numerical simulation was used to clarify the control set of parameters and comprehend the overall dynamics. For the system to continue, it was determined that extremely high levels of either fear or harvesting lead to the extinction of one of the predator species. Moreover, in contrast to the ecological assumption that if two species are vying for the same resources, population values cannot be constant, this study showed that it is possible for two competing species to subsist on the same resources.

A 90-year record of lake whitefish Coregonus clupeaformis abundances in Michigan waters of the upper Laurentian Great Lakes

Fishery managers throughout the upper Laurentian Great Lakes are currently faced with a two-decade decline in abundance and harvest of lake whitefish Coregonus clupeaformis stocks. We used multivariate auto-regressive state-space (MARSS) models to develop long-term (90-year; 1929–2018) time-series of lake whitefish relative abundance based on commercial catch-per-effort (CPE) data for 13 statistical districts in State of Michigan waters, including 1836 and 1842 Treaty ceded waters, of Lakes Superior, Michigan, and Huron. CPE time-series were used to estimate historical baseline conditions, which were compared to more recent conditions, specifically with reference to select regulatory, environmental, and ecological conditions in each lake and fishing intensity. Population growth rates suggested that lake whitefish stocks responded: (1) negatively to high levels of harvest and expansion of sea lamprey Petromyzon marinus populations during the early-1900s; (2) positively to commercial fishery regulation and sea lamprey control during the late-1950s and early-1960s; and (3) negatively to establishment of dreissenid mussels Dreissena spp. in Lakes Michigan and Huron by 2005 and the recent period of low productivity in all three lakes since the mid- to late-2000s. When placed in a historical context, the most recent (2011–2018) lake whitefish abundances are low, intermediate, and high in 31 %, 46 %, and 23 % of all districts examined. Although environmental and ecological conditions likely drove recent declines, correlation analysis suggested that higher levels of fishing intensity were associated with greater district-specific declines in abundance during the last two decades (1999–2016), a period characterized by lower overall productivity and limited recruitment in most lake whitefish stocks.

Research on Performance Evaluation Method of Rice Thresher Based on Neural Network

Because the threshing device of a combine harvester determines the harvesting level and threshing separation performance of a combine harvester, the analysis and study of the threshing device of a combine harvester is key to improving its performance. Based on the threshing device of a half-feed combine harvester, the simulation model of a discrete element threshing device is established in this paper. With the threshing drum rotation speed, feed volume, and concave sieve vibration frequency as the variable factors, the BP neural network model and linear regression equation model established for the loss rate and impurity content for two kinds of threshing performance indicators, respectively, and through the discrete element threshing performance test, two kinds of methods of threshing performance prediction are analyzed. The results show that the neural network and linear regression can be used for the threshing performance indicators, however, the BP neural network prediction effect has a better prediction precision, better reliability, and the trained neural network can be used in the general case of the threshing performance indicators. This provides a new idea for improving the threshing performance of a combine harvester.

Low Tree Vigor, Free Palmette Training Form, and High Planting Density Increase Olive and Oil Yield Efficiency in Dry, Sloping Areas of Mediterranean Regions

Exploiting biodiversity must be considered today an effective strategy to improve the sustainability of olive production systems. The evaluation of local cultivars, based on their vegetative and fruiting traits, along with an analysis of product quality, may contribute significantly to the development and diffusion of new olive-growing systems. The aim of this study was to evaluate growth, productivity, and olive oil quality of three Sicilian cultivars with different vigor/growth habit grown in four different combinations of training form and planting density. ‘Abunara’, ‘Calatina’, and ‘Nocellara del Belice’ olive trees were planted in four different intensive planting systems: 2 × 5 m trained to central leader (CLx2), 3 × 5 m trained to free palmette (FPx3), 4 × 5 m trained to small globe vase (GVx4), and 5 × 5 m trained to poly-conic vase (PVx5) and evaluated for seven years. Planting systems with low-density showed faster growth (trunk cross section area and canopy volume) than high-density systems. High-density systems had higher yield per hectare but lower yield per tree than low-density systems. ‘Calatina’ was the least vigorous but most productive cultivar. ‘Abunara’ and ‘Nocellara’ were relatively vigorous and suffered the tight spacings of high-density systems. Yield efficiency was generally high in ‘Calatina’, and it showed an increase with time in ‘Abunara’ and ‘Nocellara’ grown under the GVx4 and PVx5 systems. Fruit yield per hectare was highest in ‘Calatina’ grown under high-density systems. Oil yield was lower in ‘Nocellara’ than in ‘Abunara’ and ‘Calatina’. In terms of oil quality, ‘Calatina’ and ‘Abunara’ produced oils with higher oleic acid content than ‘Nocellara’. Generally, ‘Calatina’ has production characteristics of considerable interest, which, combined with low canopy volume and vigor, make it suitable for intensive pedestrian olive orchards with high levels of harvest and pruning mechanization and using different strategies and machines. Overall, for their management flexibility, these planting systems can contribute to improve sustainability of the olive industry even in sloping, dry areas of the Mediterranean.

Perceived and experienced constraint negotiation: do first‐time elk hunters know what they are in for?

AbstractOpportunities to hunt big game species such as elk (Cervus canadensis) are often rationed through a lottery permit system when demand for permits exceeds the population's ability to sustain harvest levels. We conducted a survey of elk hunters and would‐be elk hunters in the summer of 2016 to compare elk‐hunting constraints among 3 groups of individuals. Groups consisted of 1) individuals who possessed a landowner hunting permit at some point between 2011 and 2016 (Landowner), 2) individuals who did not possess a landowner permit but did possess a general hunting permit between 2011 and 2016 (General), and 3) individuals who had not possessed a Nebraska elk‐hunting permit of any kind between 2011 and 2016 but had attempted to draw a permit from the lottery system at least once during these years (Lottery). We used latent class regression to classify survey participants based on their responses to 7 questions related to constraints to elk hunting that were either experienced (Landowner and General) or perceived (Lottery) on a 5‐point scale (Strongly Disagree to Strongly Agree). Probability of latent class membership was estimated for each hunter group. Latent class regression revealed 6 latent classes with Landowner participants most likely to belong to classes who exhibited the least difficulty negotiating all constraints. General and Lottery participants were most likely to fall into classes exhibiting more difficulty negotiating constraints related to interactions with property owners for permissions to hunt on their land. Our findings can assist policy makers and managers with tailoring lottery permit systems, particularly in locations where most of the hunting opportunity is restricted to privately owned land.

An initial assessment of the sustainability of waterbird harvest in the United Kingdom

Abstract There is a need to assess the sustainability of wild bird harvest in the United Kingdom (UK), and more widely, across Europe. Yet, data on populations and harvest sizes are limited. We used a demographic invariant method (DIM) to estimate potential excess growth (PEG) for populations of UK wintering waterbirds and calculated a sustainable harvest index (SHI) for each. We compared this with population trends and conservation classifications (e.g. Birds of Conservation Concern [BoCC]) to assess the sustainability of harvests and the utility of these classifications. Our approach found evidence for potential overharvest of mallard Anas platyrhynchos, Eurasian teal Anas crecca, gadwall Mareca strepera, Canada geese Branta canadensis, greylag geese Anser anser and woodcock Scolopax rusticola. Whether DIM methods predict overharvest is highly dependent on estimates of maximum population growth rates inferring PEG. We found estimates of maximum population growth to be variable across a range of different methods. We found no relationship between SHI and short‐term wintering trends or conservation classification under the UK's BoCC framework. There was however a positive relationship between SHI and long‐term wintering trends. Policy implications. Our results suggest that UK‐based harvest is unlikely to be a major determinant of population trends for the majority of UK overwintering waterbirds, but harvest rates for some species may exceed that required to maintain stationary population growth. The lack of a relationship between conservation classifications and SHI strongly suggests that such conservation classifications are not an appropriate tool for making decisions about harvest management. Instead, our assessment provides the basis for a framework to make evidence‐based decisions on sustainable harvest levels in the face of incomplete data. There is currently no clear policy instrument in the UK to support such a framework via controls on either harvest effort or mortality of waterfowl. We believe such an instrument is urgently needed to ensure the UK can adapt to changing pressures and ensure the sustainable use of our wildlife populations.

Is restricting catch to young sharks only more sustainable? Exploring a controversial management strategy for bull, tiger, blue and bonnethead sharks

AbstractProper management of shark populations is an immediate concern due to their high vulnerability. In this study, we applied stochastic demographic models for four shark species (bull shark Carcharhinus leucas, tiger shark Galeocerdo cuvier, blue shark Prionace glauca and bonnethead Sphyrna tiburo) to test how population growth behaved under different exploitation scenarios, such as the exclusion of older sharks from fisheries. Populations grew at considerably slow rates when unfished, except for P. glauca. When fisheries targeted all individuals, populations started to decline at generally very low fishing mortality and harvest rates. Conversely, when adult individuals were excluded from fisheries, population resiliency increased despite higher fishing pressures, with no negative growth rates even if harvest levels were doubled. This study indicates that conservation of these species may benefit from protecting adult stocks.

The structure of optimal solutions for harvesting a renewable resource

AbstractWe consider the problem of optimal harvesting of a renewable resource whose dynamics are governed by logistic growth and whose payoff is proportional to the harvest. We consider both the case of a finite and an infinite time horizon and analyse the structure of the optimal solutions and their dependence on the parameters of the model. We show that the optimal policy can only have one of three structures: (1) maximal harvesting effort until the resource is depleted, (2) zero harvesting during an initial time interval followed by a subsequent switch to maximal harvesting effort, or (3) a singular solution, which corresponds to an intermediate level of harvesting, accompanied by the most rapid approach path. All three scenarios emerge, with minor variations, with finite and infinite time horizons, depending on the particular combination of parameters of the system. We characterize the conditions under which the singular solution is optimal and present suggestions for designing an optimal and sustainable harvesting strategy.Recommendations for Resource Managers: We have rigorously explored a standard optimal harvesting model and its steady states. We show that three different types of solutions may emerge: (i) maximal harvesting eventually leading to a complete depletion of the stock; (ii) maximal harvesting with a potential period of idleness leading to a positive stock; (iii) an initial phase of either no or full harvesting followed by a period of intermediate harvesting intensity leading to a positive stock (singular solution). With some modifications, similar results hold for a finite planning horizon. Which of these three scenarios emerges in the finite horizon case depends not only on the parameter values but also on the length of the planning horizon.

Hunting Levels of Turtle Dove (Streptopelia turtur) at Sites Where Food Is Provided: Implications for Sustainable Harvesting.

Simple SummaryThe European turtle dove (Streptopelia turtur) is an important gamebird in south-western Europe, and in some areas a significant proportion of hunting grounds conduct targeted management aiming to increase its breeding densities and hunting opportunities, mainly through food provision. Using harvest data from managed grounds, we estimated the productivity (juvenile/adult ratio), the harvesting levels and the local turtle dove abundance before the hunting season, the latter being compared to the number of birds observed by hunters in food plots. Our research found high values of productivity and significant differences between the estimated abundance and the number of birds observed by hunters, which suggests that in a high proportion of grounds, the latter method may have led to bird overestimation and overharvesting. As managed grounds for the turtle dove may increase the productivity and recruitment of the species, it is crucial to ensure sustainable harvesting through (1) bird monitoring based on transects to calculate abundance and (2) promoting regulations to adjust the number of hunting days.In some regions of Spain, hunting grounds conduct management targeting the European turtle dove (Streptopelia turtur), a commonly hunted species, and unsustainable harvesting levels at these sites have been identified as one of the factors responsible for the species’ decline across its range. In hunting grounds where food was provided, we estimated the local turtle dove abundance before the hunting season, productivity (juvenile/adult ratio) and harvesting levels using harvest data from managed grounds over 4 years (2009, 2015, 2019 and 2020). Compared to previous research, a higher productivity value was found (median 1.67, range 1.24–4.15) in grounds providing more food for a longer period. We calculated that the harvesting rate should not exceed 37% of the estimated turtle dove population size (35–45%). Significant differences were found between the estimated local turtle dove abundance using a removal sampling protocol and the number of birds observed by hunters before the hunting season, which suggests that in a high proportion of grounds, the latter method may have led to bird overestimation and overharvesting. Our research supports the current European Union’s harvest management plan to promote sustainable hunting in grounds where targeted management is conducted.

In situ conservation challenges of Brackenridgea zanguebarica Oliv.: A South African case study

Abstract. Rasethe MT. 2022. In situ conservation challenges of Brackenridgea zanguebarica Oliv.: A South African case study. Biodiversitas 23: 3876-3883. This qualitative study probed the factors that are hindering the successful management of Brackenridgea zanguebarica Oliv, a South African plant that is listed as Critically Endangered on the South African Red Data List. The plant is restricted to one state-owned nature reserve in the Limpopo province, South Africa. Brackenridgea zanguebarica is a threatened medicinal plant sought after by laypeople and traditional healers and often found in muthi markets across South Africa. In this country, this species is confined to the Thengwe village in the Vhembe district of the Limpopo province. Information on this species was collected using semi-structured questionnaires and focus group discussions during face-to-face interviews with all conservationists employed in the state-owned nature reserve. The interviews were complemented by extensive field observation on the population status of B. zanguebarica across the reserve. The results showed that B. zanguebarica is mainly being managed using environmental regulations and patrols in reserve to arrest and charge persons found in the reserve harvesting B. zanguebarica. The reserve only has seven permanent officials. They do their work without firearms to protect themselves from poachers and no cars are used during patrols due to the lack of proper roads in the mountainous area. The conservation officers mentioned that there is always new evidence of illegal harvesting of B. zanguebarica across the nature reserve. Field observation of the harvested populations indicated high levels of unsustainable harvesting. The harvesting reported by conservation officials and observed is of concern and will increase the risk of extinction of this species. The implementation of regulations as the sole management tool for this species in the Brackenridgea Nature Reserve is not enough, resulting in a situation where the current management of B. zanguebarica in reserve is not effective.

Assessing cross-regional flows of economic benefits: A case study of Pacific halibut commercial fishing in Alaska

The economic effects of changes to harvest levels can be far-reaching. Fisheries management policies that alter catch limits have a direct impact on harvesters, but at the same time, there is a ripple effect through the economy. To bring a better understanding of the magnitude of this multiplier effect, this paper applies multiregional economic impact assessment to the case study of Pacific halibut commercial fishing in Alaska.The results suggest that the revenue generated by Pacific halibut at the harvest stage accounts for only a fraction of economic activity that would be forgone if the resource was not available to fishermen. However, the adoption of a multiregional approach to the economic impact assessment highlights that a myriad of economic benefits in this case are realized far from where the resource is harvested. This results from strong economic ties the Alaskan fishing activities have to the economy of the rest of the United States, be it through trade, nonresident workforce or out-of-state investment in production factors such as fishing quotas.

Impacts of harvesting methods on nutrient removal in Dutch forests exposed to high-nitrogen deposition

ContextForest harvest removal may cause nutrient depletion of soils, when removal of essential nutrients, including nitrogen (N), phosphorus (P), sulphur (S), calcium (Ca), potassium (K) and magnesium (Mg) exceeds their net input by deposition and weImpacts of acid atmospheric deposition on woodland athering minus leaching. Nutrient removal by harvest depends on tree species and the harvesting method, i.e. whole-tree harvesting (removal of stems and branches) versus stem wood removal only.AimThe aim of this study was to assess the impacts of these two harvesting methods on nutrient removal in Dutch forests exposed to high-nitrogen deposition.MethodsTo assess those impacts, we measured nutrient concentrations in stem wood and branch wood of seven major tree species in the Netherlands, i.e. Japanese larch (Larix kaempferi Lamb.), Norway spruce (Picea abies L. Karst.), Douglas fir (Pseudotsuga menziesii Mirb.), Scots pine (Pinus sylvestris L.), silver birch (Betula pendula Roth), beech (Fagus sylvatica L.) and common oak (Quercus robur L.). Average nutrient concentrations in stems were based on measured concentrations in heartwood, sapwood and bark and estimated volumes and densities of these compartments. Similarly, average nutrient concentrations in branches were based on measured concentrations in coarse branches, fine branches and the bark of coarse branches and estimated volumes and densities of these compartments. Removal was assessed by using the average growth rates of these tree species on nutrient poor sandy soils in the Netherlands.ResultsCompared to other countries, N concentrations in the Netherlands were higher in stems, while phosphorus, Ca, K and Mg concentrations in both stems and branches were nearly always lower. The elevated long-term N deposition levels in the Netherlands most likely contribute to this finding, since N deposition causes soil acidification reducing the availability of Ca, K, Mg and P, that could become limiting to growth. Limits for sustainable harvest, above which outputs exceed inputs of nutrients, depend on nutrient, soil type and tree species and are mostly determined by K and P and sometimes Ca, which may already be depleted at relatively low harvest levels on poor sandy soils, in particular for broadleaved species, while depletion of Mg is not likely. Nevertheless, the average growth of forests in the Netherlands appears to be slightly higher than in most other countries in Europe.ConclusionOverall, we thus conclude that limited P, Ca, Mg and K availability in response to elevated N deposition is reflected in reduced contents of these nutrients in stem wood and branch wood but not in growth.Key messageNutrient concentrations in tree compartments were assessed for seven major tree species in the Netherlands. Concentrations of phosphorus, calcium, potassium and magnesium (base cations) in stems and branches are mostly lower compared to those in other countries, while nitrogen concentrations are higher. A long-term nitrogen deposition has likely contributed to these differences. The average growth has not declined, despite the low availability of phosphorus and base cations. Limiting the harvest of branch wood is suggested on nutrient poor soils to avoid depletion of phosphorus and base cations.

Harvesting has variable effects on demographic rates and population growth across three dry forest tree species

AbstractUnderstanding how anthropogenic activities, such as harvesting, influence plant populations is important to quantify sustainable practices that conserve species of socioeconomic importance. There is limited knowledge on how harvesting of branches and non‐timber forest products affect populations of trees in the dry tropics. We measure demographic vital rates of three dry tropical tree species in the presence and absence of harvesting and apply integral projection models to quantify population growth rates, which represent the mean fitness across the life cycle. Our results show that the three species vary in their demographic rates and life history. Harvesting significantly decreases the growth of two species. Current levels of harvesting only significantly decreased the population growth rate of one species that experienced both branch and main stem harvesting. Life table response experiments reveal that the negative effect of harvesting on the population growth rate of this species is primarily due to individuals being forced to re‐sprout from their base. Few individuals were observed recruiting from seed, and this might be due to the presence of other threats, such as fire, soil erosion, and grazing. Our results provide knowledge on the demography and the effects of harvesting on endemic tree species of the Eastern Ghats, a region for which few demographic studies are available. These results are relevant to conserving forest biodiversity for the benefits of people and can contribute to quantitative threat assessment for IUCN red listing.

Identifying overexploitation in the coastal Greenland halibut fishery in the Disko Bay using static bioeconomic modelling

The North Atlantic Fisheries Organization (NAFO) has continuously lowered their advice regarding the Total Allowed Catch (TAC) for the coastal Greenland halibut fisheries in Western Greenland. This is due to concerns of overexploitation of the fishery. This paper investigates how the fishing intensity in the fishery for Greenland halibut (Reinhardtius hippoglossoides) in the Disko Bay, Greenland, affects the current and future income opportunities of coastal fishers. Through bio-economic modelling, I find presence of economic overexploitation of the Greenland halibut fish stock in the Disko Bay. Specifically, the actual Greenland halibut stock in 2019 is found to constitute only 56 pct. of the economic optimal stock size in the baseline scenario. The actual profit is almost 40 million DKK lower than the optimal profit due to higher costs of harvesting, which arise because the actual stock size is lower than the optimal and because of a suboptimal split of the TAC between vessels (above 6 m in length) and boats (6 m or below in length) in the fishery. The results presented in this article show that there is significant scope for economic optimization of the coastal Greenland halibut fishery through a temporary reduction in harvest of Greenland halibut to regenerate the stock to its optimal size and a transfer of TAC from the boat segment to the vessel segment. Notably, this article does not find that the stock of Greenland halibut in the Disko Bay is further decreasing at current (2019) harvest levels, however, this finding is contingent on the length of the data series used for the estimation of the growth model.

Carbon removals from nature restoration are no substitute for steep emission reductions

Carbon removals from nature restoration are no substitute for steep emission reductions