The generation of energy through anaerobic digestion using animal manures is being promoted as an environmentally sustainable method of managing animal wastes. However, sustainability of biogas production is reliant on the sustainable utilization of the digestates that emanate from the process. Our study evaluated the effects of the biogas digestates on crop phytotoxicity and their fertilizer potential as a nutrient solution in hydroponic tomato production. Biogas digestates diluted up to 40% (v/v) resulted in significantly (P < 0.05) the lowest relative seed germination (RSG) in all vegetables evaluated in our study. The highest RSG was observed in the 10% biogas digestates, which was higher than the control treatment. For the crop growth study, relative to the control,the treatments with 20%, 40% and 60% mineral fertilizer substitution resulted in 39.4%; 22.8% and 8.7% significantly (P < 0.05) lower chlorophyll content, respectively. On average, the treatments with biogas slurry, though substituted with mineral fertilizers, resulted in a 275% lower fresh fruit yield compared to the control treatment. However, with biogas digestates, the sugar content in the tomato fruits significantly increased, whilst the heavy metal content was below that recommended limit when irrigation water is used. The results of our study demonstrated that cow based digestates are not a suitable nutrient media for hydroponic tomato production. Moreover, even with mineral fertilizer supplementation, only the control treatment containing only mineral hydroponic fertilizer resulted in positive growth and yield in tomatoes.

Elevated trace metal in the aquatic environment is a global challenge. In this investigation, copper (Cu) levels were assessed using inductively coupled plasma optical emission spectrometry (ICP-OES) during winter and summer months of 2012. The aim of this study was to determine the pollution status of Central Namibian coastline using copper levels in black mussel, sediments and water as indicators. Results indicated that Cu levels were significantly higher at Walvis Bay Harbour in mussels, sediments and water column (P < 0.05). Levels between summer and winter were not significant (P > 0.05). Black mussels at Walvis Bay Harbour could be regarded safe for consumption as the recorded levels were within the permissible limit set by the European Commission (EC. No.466/2001). However, further monitoring of the coastline is ecologically imperative to avoid human risks and irreversible ecological impacts.

Namibia is the most arid country in sub-Saharan Africa characterized by the existence of two deserts, the Namib and the Kalahari. However, though being arid, agriculture still plays a critical role in Namibia’s economy, which includes both crop and animal production. Furthermore, the country is endowed with vast marine resources, with its marine waters being equivalent to two-thirds of Namibia’s terrestrial environment. In the face of climate change and a growing population, there is a need for Namibia to continue with its climate smart efforts which is critical in shifting the country from its current dependency on imports thus increasing the country’s food self-sufficiency. This chapter highlights the threats posed by climate change, both on land and the marine environment of the country, which has potential negative impacts on the economy. Current research being undertaken in Namibia on ocean acidification, sea water harvesting, climate smart agriculture, and atmospheric science, is also highlighted in this chapter. The information presented in this chapter will be critical in guiding climate change mitigation policies in hyperarid African countries, thus reducing the burden caused by the global change in climate. Aspects on the direction of future research on climate adaptation with a holistic and multidisciplinary approach are also proposed.

This study investigated the effects of oregano (Origanum vulgare) essential oil (OEO) anaesthesia and stress-related physiological parameters in tilapia mossambicus (Oreochromis mossambicus) post-juveniles. Fish were subjected to different concentrations of OEO (25, 50, 100, and 150 μL L−1) to assess the effects of the anaesthesia and recovery time. A second experiment subjected fish to other handling treatments, including a control (no OEO exposure), ethanol solution, 25 μL L−1 (low effective anaesthesia concentration of OEO), and 100 μL L−1 high effective anaesthesia concentration of OEO) for 10 min to assess the haemato-biochemical indices and survival rate at 0 h and after 24 h. Moreover, all the tested OEO concentrations induced anaesthesia in the studied fish, where the anaesthesia induction time decreased with increased OEO concentrations. Meanwhile, the inverse was reported for recovery time. Based on the ideal anaesthetic criteria, 50 μL L−1 and 100 μL L−1 were the suitable concentrations that could be recommended for quick anaesthesia. However, according to the haemato-biochemical parameters and survival results, 25 μL L−1 was safe to anaesthetise tilapia mossambicus for 10 min and could be recommended for time-consuming fish-handling procedures. Future studies should investigate multiple factors that influence anaesthesia in fish for better optimisation of OEO in tilapia mossambicus.

Namibia is the most arid country in sub-Saharan Africa characterized by the existence of two deserts, the Namib and the Kalahari. However, though being arid, agriculture still plays a critical role in Namibia’s economy, which includes both crop and animal production. Furthermore, the country is endowed with vast marine resources, with its marine waters being equivalent to two-thirds of Namibia’s terrestrial environment. In the face of climate change and a growing population, there is a need for Namibia to continue with its climate smart efforts which is critical in shifting the country from its current dependency on imports thus increasing the country’s food self-sufficiency. This chapter highlights the threats posed by climate change, both on land and the marine environment of the country, which has potential negative impacts on the economy. Current research being undertaken in Namibia on ocean acidification, sea water harvesting, climate smart agriculture, and atmospheric science, is also highlighted in this chapter. The information presented in this chapter will be critical in guiding climate change mitigation policies in hyperarid African countries, thus reducing the burden caused by the global change in climate. Aspects on the direction of future research on climate adaptation with a holistic and multidisciplinary approach are also proposed.