Does a reduction in the price of rhino horn prevent poaching?

Rhino poaching around the world has increased inordinately, to the extent that concerns exist over the possible survival of the species. An open access rhino poaching model is developed for South African rhino. The model is a hybrid dynamical model, as both a system dynamics model as well as a Bayesian network model are developed. The system dynamics model is used to estimate the unknown parameter values (through optimisation) and also to determine the intervals for the parameters. These intervals are then used in the Bayesian Belief Network model to assess uncertainty. Hybrid approaches improve the ability to validate models compared with conventional modelling. The resultant model indicates that reducing the price of rhino horn would not be effective at curbing poaching, unless poacher costs are also increased. However, increasing poacher costs is not a realistic policy option since these costs are largely beyond the control of decision-makers. The insensitivity of price to poaching effort has implications for methods proposed to reduce the value of rhinos, such as introducing synthetic rhino horn and the de-horning of rhinos.The National Research Foundation and DEA: NRM.http://www.elsevier.de/jnc2018-09-30hj2017Economic

Financing active restoration in South Africa : an evaluation of different institutional models

The restoration of natural capital is increasingly becoming important to counter ongoing land degradation. The Natural Resource Management programme of the Department of Environmental Affairs (DEA: NRM) has long been investing in options to improve the effectiveness of active restoration. The aim of this study is to conduct a cost-benefit analysis of two approaches to active restoration at selected sites in KwaZulu-Natal, South Africa. This study compares a barter approach to a financial compensation approach, both of which are used to finance and advance active restoration. The barter system relies on community members to grow various tree seedlings, and they then receive various goods in exchange for the seedlings grown, whereas the financial compensation sources the seedlings from various commercial nurseries. We use a system dynamics model to evaluate the benefits and costs of these restoration approaches. The main finding is that restoration through the reintroduction of indigenous trees contributes a great deal towards increased carbon sequestration, with the barter option marginally cheaper than the nursery option. The model estimates an annual saving of more than R120 000 per annum with the barter approach in terms of the total restoration costs. However, the financial saving is not significant, as the model concludes that the financial compensation approach is more economically attractive considering a broader range of variables. The model estimated the value of water lost to be -R2 929 992.14 for the financial compensation model and -R2 920 412.76 for the barter financing model over 30 years. With the financial compensation model, the rate of clearance was found to be higher, thus translating directly into a greater accumulation of benefits. The lesser losses in water value, coupled with the higher gains in value-added products for the financial compensation model, are the main reason the financial compensation model is the more economically attractive financing approach.The Department of Environmental Affairs (DEA) and the Working for Water programme.http://www.aaae-africa.org/afjaream2018Economic

Aquatic weeds : to control or not to control. the case of the Midmar Dam, KwaZulu-Natal, South Africa

The Midmar Dam within the uMngeni Catchment, KwaZulu-Natal is important for water provisioning and recreational use. In 2014, an estimated 60 ha of the dam was infested with Egeria densa, which can spread at a rate of 50% per annum under optimal conditions. E. densa limits access to, and the recreational use of, the dam. We use the travel cost method to estimate the recreational value of the Midmar Dam, informing the maximum desirable cost of control. The model estimates that the most likely extent of the invasion would be between 233 ha and 771 ha. The estimated cumulative NPV is R684 million for the best-case scenario, which allows for clearing operations and a spread rate of 15%. If no clearing is done, the cumulative NPV is reduced to an estimated -R20 million. This study therefore suggests that management of the problem is imperative, but that control efforts should not exceed R687.8 million over 30 years. Doing so will constitute a net loss to society.The DEA: NRM programmehttp://www.aaae-africa.org/afjaream2018Economic

An economic analysis of different land-use options to assist in the control of the invasive Prosopis (Mesquite) tree

The invasive Prosopis spp. tree is one of the major causes of disturbance affecting the Orange River water management areas in the Northern Cape, South Africa. These disturbances affect natural capital, such as reducing the stream flow of the Orange River, causing a decline in biodiversity of the native Nama Karoo vegetation, consuming excessive water, and invading dryland areas. Therefore, we assessed the economic value of different land-use options following the control of Prosopis spp. to prevent re-invasion using a system dynamics model. This study yields positive cumulative NPVs of between ZAR28.3 million and ZAR98.3 billion when co-finance of between 20% and 100% is included to clear the Prosopis spp., combined with the productive land use of the cleared land by the private sector. This is in stark contrast to a negative NPV of -ZAR11.6 million when no alternative land-use activity is implemented on the cleared land. This study shows empirically that clearing Prosopis spp. and restoring the cleared land for agricultural land-use options is a costeffective strategy for controlling the invasive Prosopis spp. trees.The Natural Resources Management programme of the Department of Environmental Affairs (DEA: NRM).http://www.aaae-africa.org/afjaream2018Economic

An assessment of the costs and benefits of using Acacia saligna (Port Jackson) and recycled thermoplastics for the production of wood polymer composites in the Western Cape province, South Africa

Acacia saligna (Port Jackson) is one of the most pervasive IAPs in South Africa. The government’s control efforts have by and large not been co-financed by the private sector due to a lack of incentives. Here we develop a system dynamics model to assess the costs and benefits of using the invasive Acacia saligna for the production of wood polymer composites (WPCs). The cumulative net present value for clearing Acacia saligna and making WPCs amounts to approximately ZAR122.1 million for the baseline scenario (no WPC production), and is estimated to be ZAR144.4 million for Scenario 2 (WPC production with 20% co-financing), ZAR172.7 million for Scenario 3 (50% co-financing) and ZAR211.2 million for Scenario 4 (100% co-financing). In addition to these direct financial benefits, the control of Acacia saligna also offers benefits with respect to employment, an increase in the state’s tax revenue base, and an increase in the contribution to GDP.The Department of Environmental Affairs (DEA) and the Working for Water programme.http://www.aaae-africa.org/afjaream2018Economic

An assessment of the potential economic impacts of the invasive polyphagous shot hole borer (Coleoptera: Curculionidae) in South Africa

Studies addressing the economic impacts of invasive alien species are biased towards ex-post assessments of the costs and benefits of control options, but ex-ante assessments are also required to deal with potentially damaging invaders. The polyphagous shot hole borer Euwallacea fornicatus (Coleoptera: Curculionidae) is a recent and potentially damaging introduction to South Africa. We assessed the potential impact of this beetle by working across economic and biological disciplines and developing a simulation model that included dynamic mutualistic relations between the beetle and its symbiotic fungus. We modeled the potential growth in beetle populations and their effect on the net present cost of damage to natural forests, urban trees, commercial forestry, and the avocado industry over 10 yr. We modeled high, baseline, and low scenarios using discount rates of 8, 6, and 4%, and a plausible range of costs and mortality rates. Models predicted steady growth in the beetle and fungus populations, leading to average declines in tree populations of between 3.5 and 15.5% over 10 yr. The predicted net present cost was 18.45 billion international dollars (Int. $), or about 0.66$2.7 billion to $164 billion for low and high scenarios). Most of the costs are for the removal of urban trees that die as a result of the beetle and its fungal symbiont, as has been found in other regions. We conclude that an ex-ante economic assessment system dynamics model can be useful for informing national strategies on invasive alien species management.The Department of Science and Innovation-National Research Foundation (DSI-NRF) Centre of Excellence for Invasion Biology and the Centre for Biological Control at Rhodes University as well as the Oppenheimer Memorial Trust and the Millennium Trust.https://academic.oup.com/jeehj2023BiochemistryForestry and Agricultural Biotechnology Institute (FABI)GeneticsMicrobiology and Plant Patholog

The effect of accessibility and value addition on the costs of controlling invasive alien plants in South Africa: A three-species system dynamics model in the fynbos and grassland biomes

We developed a two-biome (grasslands and fynbos) system dynamics model simulating invasions of three invasive alien plant species - black wattle (Acacia mearnsii) and two pine species (Pinus patula and Pinus pinaster) - and some of the consequences. The model considers three components: invasion dynamics; revenue from the sale of woody products derived from clearing invasive alien plants; and a coefficient that models the effect of increased accessibility to invaded areas. The model shows that increasing the returns on value added products (VAPs) from invasive alien plants (IAPs) by between 70% and 130% results in positive nett present values (NPVs) of R2.7 million for P. patula, R151.7 million for P. pinaster and R115.9 million for A. mearnsii (1996 base year). At the same time, the invasion of these species is reduced dramatically by 2025. The results show that there is much scope, and indeed a clear requirement, for improved returns on investment from harvesting these species through increasing the returns from VAPs. However, accessibility to invaded areas would need to be increased for positive nett gains in water yields and other returns to be maximised

A bioeconomic analysis of bushmeat hunting

Unsustainable bushmeat hunting is a major threat to mammal species, particularly in West/Central Africa. We developed a multispecies dynamic simulation model of hunter behaviour, parameterized using data from the Ashanti region, Ghana. The model distinguishes between two hunting techniques, snaring and gun hunting. We analyse the impact of key economic parameters on off-takes. Economic incentives determine the effort devoted to hunting, the choice of hunting technique, and the species that are consumed domestically or traded in markets. These factors, together with the growth rates and catchabilities of hunted species, determine the ecological impact of hunting. The results suggest that increased bushmeat prices are likely to lead to a switch from snaring, which is cheaper but less efficient, to gun hunting, with a consequent impact on vulnerable species. Increases in agricultural prices have an ambiguous effect on hunter behaviour, depending on the balance between incentives to invest in agriculture and increased consumption as incomes improve. Penalties are more effective if they target bushmeat sales, rather than the act of hunting. This model represents a step forward because it explicitly considers bushmeat as a component of the household economy. This has important implications as regards the development of policies to conserve species hunted for bushmeat

The demand for ecosystem services by different calf-production systems in South Africa

This study compares the environmental impact (i.e. feed intake, water consumption and greenhouse gas emissions) of 12 different calf-production systems to produce a calf weighing 190 kg to 220 kg. A farm-level static model and a national-level dynamic model were both developed to consider the variation in the environmental impact following different cattle management protocols. It was found that aspects related to calf mortality rates, calving percentage, average daily gain and fodder conversion ratios play a significant role in the total environmental impact of calf production. The longer it takes for a calf to reach the target weight and the more animals there are in the herd structure, the higher the environmental impact and the more unsustainable the production becomes. Therefore, the higher the environmental impact, the higher the relative environmental impact to produce a kilogram of beef. This requires a careful yet decisive policy focus and action plan towards sustainable rangeland management.http://www.aaae-africa.org/afjaream2018Economic

The effect of rainfall variability on sustainable wheat production under no-till farming systems in the Swartland region, South Africa

Twenty years ago it was argued that rotational wheat production systems will reduce the economic risks to farmers and restore soil quality. Here we reflect on this assertion by analysing the evidence of a 12-year data window within a trial on a mixture of crop rotation systems at Langgewens Research Farm, South Africa. It was been found that production systems that include rotations with medics and/or medic-clover show some potential for improvement compared with wheat only, with a combination of the annual legume pasture with an added saltbush pasture showing the greatest improvement when taking into consideration the benefits from livestock production that are derived from pastures. Pastures are more resilient to changes in rainfall compared with wheat only. Planting pastures in alternate years also improves the yields from wheat, and this is beneficial in periods of low rainfall. Rotation systems on this farm that include lupin perform worse than the wheat-only model. Furthermore, when modelling the effect of drought on the system, the results of the multi- and rotation production systems actually improve.http://www.aaae-africa.org/afjaream2018Economic