Nature-based solutions in the savanna belt of Africa: Insights from a systematic review

King P., Martin-Ortega J., Armstrong J., Ferré M., Bark R.H.

Kuyah S., Buleti S., Dimobe K., Nkurunziza L., Moussa S., Muthuri C., Öborn I.

The size of drylands in Africa is constantly increasing following the increase of the population, land use and practices used in the daily activities to sustain community livelihood. Climate change and erratic weather conditions are also expected to contribute to further land degradation, expanding dryland ecosystems. Land degradation undermines the range of ecosystem services on which dryland communities depend on. This chapter highlights challenges faced by dryland communities in Africa, which might be exacerbated by climate change. Throughout the chapter, evidence is presented on ways to transform drylands into productive, profitable and sustainable ecosystems that contribute to climate change adaptation and mitigation. A very popular approach is famer-managed natural regeneration (FMNR), which has a number of advantages over other approaches in the context of drylands. FMNR has been actively promoted in the Sahel for over four decades, spreading from Niger to the neighbouring Burkina Faso and Mali in the 1980s and currently to other regions in Africa and Asia. FMNR is farmer driven and creates multifunctional landscapes that offer multiple ecosystem services. At the adaptation level, FMNR restores the degraded ecosystem services such as the provision of goods to local communities facing shocks and creation of resilient production systems against extreme weather events. At the mitigation level, FMNR contributes to carbon sequestration in plant biomass and soils while reducing greenhouse gas emissions. The chapter concludes with two cases of FMNR illustrating the benefits to dryland communities.

Woroniecki S., Spiegelenberg F.A., Chausson A., Turner B., Key I., Md. Irfanullah H., Seddon N.

Dimobe K., Ouédraogo K., Annighöfer P., Kollmann J., Bayala J., Hof C., Schmidt M., Goetze D., Porembski S., Thiombiano A.

• We modelled the potential current and future distribution of Pterocarpus ernaceus in Burkina Faso. • Two scenarios (RCP 4.5 & RCP8.5) and two models (CNRM-CM5 and HadGEM2-CC) were selected. • Suitable habitats under protected areas will decline up to 61% (RCP 8.5) by 2070. • Implementation of a conservation program is required to save the species in its native range. Species distribution modelling is gaining popularity due to significant habitat shifts in many plant and animal species caused by climate change. This issue is particularly pressing for species that provide significant ecosystem goods and services. A prominent case is the valuable African rosewood tree (Pterocarpus erinaceus ) that is threatened in sub-Saharan Africa, while its present distribution, habitat requirements and the impact of climate change are not fully understood. This native species naturally occurs in various savanna types, but anthropogenic interventions have considerably reduced its natural populations in the past decades. In this study, ensemble modelling was used to predict the current and future distribution potential of the species in Burkina Faso. Fifty-four environmental variables were selected to describe its distribution in the years 2050 and 2070 based on the greenhouse gas concentration trajectories RCP4.5 and 8.5, and the general circulation models CNRM-CM5 and HadGEM2-CC. A network of protected areas in Burkina Faso was also included to assess how many of the suitable habitats may contribute to the conservation of the species. The factors isothermality (31%), minimum temperature of coldest month (31%), pH in H 2 O at horizon 0–5 cm (11%), silt content at horizon 60–100 cm (9.2%) and precipitation of warmest quarter (8%) were the most influential distribution drivers for the species. Under current climate conditions, potentially highly suitable habitats cover an area of 129,695 km 2 , i.e. 47% of Burkina Faso. The projected distribution under RCP4.5 and 8.5 showed that this area will decrease, and that the decline of the species will be pronounced. The two models used in this study forecast a habitat loss of up to 61% for P. erinaceus . Hence, development and implementation of a conservation program are required to save the species in its native range. This study will help land managers prioritise areas for protection of the species and avoid introducing it to inappropriate areas unless suitable conditions are artificially created through the management options applied.

Tovihoudji G.P., Diogo R.V., Abiola W.A., Akoha F.B., Godau T.

Low land productivity is a major constraint facing agriculture in sub-Saharan Africa, which severely affects crop yields, particularly cotton which is main export agricultural produce of Northern Benin. To overcome this situation, the hill-placement of microdose biochar-compost-based amendments was carried out at two research stations and on farmer's fields in three agroecological zones of northern Benin. The study aims to evaluate the agronomic and economic performance of cotton under two types of compost and biochar-based amendments. On stations, the experimental design used was a complete randomized block with one factor and ten treatments replicated four times as follows: (i) absolute control without any amendment (Ck), (ii) mineral fertilizer (MF) at 200 kg/ha, (iii) cow dung-based compost at 200kg/ha (CP1_200) and (iv) 300kg (CP1_300), (v) household waste-based compost at 200kg/ha (CP2_200) and (vi) 300 kg (CP2_300), the combination of CP1 and 15% biochar designated Terra preta (TP) applied at 200kg/ha (vii, TP1_200) and 300kg/ha (viii, TP1_300), the combination of CP2 and 15% biochar applied at 200kg/ha (ix, TP2_200) and 300kg/ha (x, TP2_300). On-farms, the experimental design was a randomized complete block with one factor and six optimal treatments extracted from the on-station experiments with three replicates installed in four farmers' fields from each location studied. The six treatments were: Ck, MF, CP1_200, CP2_200, TP1_200 and TP2_200. Cotton growth (Plant height, number of vegetative and reproductive branches and total bolls per plant) and yield data were collected. The treatment TP1_300 yielded higher cotton seed with 2.53 t/ha, i.e., 86% more than the absolute control. However, the highest plant growth parameters were obtained with MF which were similar to those obtained with TP1_300 (P > 0.05). Likewise, at farms, the highest plant growth parameters and yield were observed with MF followed by TP1_200 (with a cotton seed yield increase of 146% compared to the control, P < 0.05). In addition, no significant differences were observed between organic fertilizers treatments for growth variables. However yield differences occurred. To resume, TP1_300 kg/ha performed best in terms of growth and yield in on-station experiments, while on-farms, TP1_200 kg/ha produced the highest responses of cotton. Value Cost Ratio (VCR) and Benefit Cost Ratio (BCR) values were generally as good or even better for MF treatment and treatments involving CP1 at both on station and on farm, compared to Ck. Although applying mineral fertilizer (MF) alone as currently done by many farmers appears to make economic sense, this practice is unlikely to be sustainable in the long term. Applying TP1_200 and TP1_300 are two possible strategies that are affordable to farmers and provide returns on investment at least as good as the current practice of sole application of MF. However, a long-term study to assess the effect of compost-activated biochar on crop productivity and soil quality is advised.

Guyassa E., Frankl A., Jacob M., Zenebe A., Damtew A., Tolera M., Descheemaeker K., Poesen J., Nyssen J.

Nyadzi E., Werners S.E., Biesbroek R., Ludwig F.

The livelihood of many farmers across the globe is affected by climate variability and change. Providing weather and seasonal climate information is expected to support farmers to make adaptive farming decisions. Yet, for many farmers, scientific forecast information provided remains unreliable for decision-making. Scholars have called for the need to integrate indigenous and scientific forecasts to improve forecast information at the local level. In Northern Ghana, scientific forecast information from meteorological agency is unacceptable to farmers, making them rely on indigenous forecasts for adaptive decisions. This study proposed an integrated probability forecasting (IPF) method that integrates indigenous and scientific forecasts into a single forecast. As a proof of concept, we tested the reliability of IPF using binary forecast verification method and evaluated its acceptability to farmers through internally consistent multiple-response questions. Results of the reliability test show that IPF performed on average better than indigenous and scientific forecasts at a daily timescale. At the seasonal timescale, IPF and indigenous forecast performed better than Scientific forecast, although in terms of probability IF showed better results overall. Majority of the farmers (93%) prefer the IPF method as this provides a reliable forecast, requires less time, and at the same time resolves the contradictions arising from forecast information from different sources. The results also show that farmers already integrate (complementary) scientific and indigenous forecasts to make farming decisions. However, their complementary approach does not resolve the issue of contradictory forecast information. From our proof of concept, we conclude that integrating indigenous and scientific forecasts can potentially increase forecast reliability and uptake. • Forecasts information from different sources are often contradictory, affecting farmers decision making. • Combining indigenous and scientific forecast can potentially improve reliability and usefulness of forecast information. • Integrated forecast has far greater acceptability potential among farmers. • Integrated probability forecasting method ensures co-production of forecast information.

Melanidis M.S., Hagerman S.

Nature-based Solutions (NbS) are increasingly proposed in international environmental governance settings to address the interlinked crises of climate change, biodiversity loss, and growing inequality. Thus far, scholarly research on NbS has been largely conceptual, and empirical research from the social sciences is widely absent, as are insights into the narratives that surround them. Using the 2019 United Nations Climate Action Summit and the 2019 United Nations Climate Change Conference (COP 25) as a case study, we set out to analyze the range of narratives associated with proposals for (and against) NbS. We used a discourse coalition approach, drawing data from a systematic document analysis of public-facing texts from a range of actors, and expert interviews. Results reveal two central and opposing NbS narratives: 1) Leveraging the power of nature —NbS are multifunctional, powerful, and must play a critical role in addressing global challenges, especially climate change (held by NbS proponents): and 2) Dangerous distraction —NbS are being co-opted to continue with what is seen as the unsustainable, unjust, status-quo (held by NbS critics). Both narratives make use of the ambiguity of NbS, though in contrasting ways, and their respective coalitions reflect and reproduce existing fault-lines in international environmental governance. Our findings indicate that, despite its promise, ‘NbS’ is currently unable to foster inclusive participation and support transformative change. • Two central and opposing narratives characterize Nature-based Solutions (NbS) discourses. • Proponents position NbS as key to addressing climate change and bridging siloes. • Critics warn that NbS are being co-opted to maintain the status-quo. • Ambiguity is leveraged implicitly and explicitly across NbS narratives. • NbS narratives reflect and reproduce longstanding power asymmetries.

Asei R., Abaidoo R.C., Opoku A., Adjei-Nsiah S.

Studies have shown that the continuous application of N, P, and K fertilizers has led to the depletion of secondary and micronutrients, which have become limiting nutrients hindering crop growth and yield. An on-farm trial was conducted to determine the effect of site-specific nutrient fertilizers and compost on soybean yield, phosphorus use efficiency, and soil properties, at Nyong Guma, Serekpere, Daffiama Saapare, and Naaga in northern Ghana. Nine (9) treatments (3 rates of mineral fertilizer × 3 rates of FertiSoil) were applied in a factorial combination arranged in randomized complete block design with three replications. On average, the soybean grain yield increased significantly with the combined application of FertiSoil and mineral fertilizer at full rates at Nyong Guma, Serekpere, and Naaga from <1,000 kg ha−1 to > 1,500 kg ha−1. The co-application of 50% recommended rate (RR) of mineral fertilizer and 5 t ha−1 FertiSoil increased soybean grain yield by over 250% at Daffiama Saapare. The application of 50% RR mineral fertilizer significantly increased phosphorus use efficiency by 5–55% compared to its combination with FertiSoil or FertiSoil alone at different rates across locations. Incorporation of 5 t ha−1 FertiSoil and 100% RR mineral fertilizer significantly increased exchangeable K, Ca, and Mg, and microbial C and P by 0.33, 2.84, 0.56 cmol(+) kg−1 and 102.7, 33.37 mg kg−1, respectively, at Serekpere. The combined application of 5 t ha−1 FertiSoil and 50% RR mineral fertilizer relatively increased soil organic C (42%) and available P (12%) at Naaga. The soil quality index revealed that the addition of 5 t ha−1 FertiSoil to 100% RR mineral fertilizer was the most sustainable nutrient management option across the study sites. Sole mineral fertilizer treatments at 50% RR were the most profitable in all the study locations ranging from value cost ratio (VCR) of 2.7–7.6. The application of limiting nutrients and organic amendments serves as an efficient nutrient management option to improve soil health, crop production and economic profitability on smallholder non-responsive soils.

Sumberg J.

This paper introduces the Outlook on Agriculture Special Issue on biomimicry and nature-based solutions. It provides a selective overview that will help frame and situate the collection, with a particular focus on agriculture and food production. The relationship between agriculture and nature is a central concern, and particularly how this relationship is framed by those promoting the idea that to overcome the multiple challenges it faces, agriculture must (re)turn to nature. The significance of different understandings of ‘nature-based solutions’, and the relative importance of biomimicry, are explored.

Nigussie A., Haile W., Agegnehu G., Kiflu A.

Although numerous factors contribute to wide yield gaps, low external inputs, particularly N, and poor cropping practices such as soil tillage and monocropping are among the major factors affecting low maize production. In view of this, field experiments were implemented on two sites with Cambisols and Chernozem soil types in two consecutive years to evaluate the impacts of different soil management practices on the grain yield and quality, nitrogen uptake, and selected soil properties. A three-factor experiment was arranged as a split-split plot arrangement randomized complete block design with three replications. The minimum tillage (MT) and conventional tillage (CT) were used as the main plot, haricot bean-maize rotation and maize monocropping were used as the subplot, and four levels of nitrogen fertilization (control, 20 t ha-1 compost, 46 kg N ha−1 + 10 t ha−1 compost, and 92 kg N ha−1) were used as the sub-subplot. Analysis of variance showed that soil management practices were significantly affecting grain yield, N-uptake, and soil properties. In sites, the conventional tillage and rotation system increased the grain yield and N-uptake in contrast to the minimum tillage and monocropping, respectively. Similarly, nitrogen evidently affected the grain yield, N-uptake, and selected soil properties. However, tillage methods differed in their effects on soil chemical properties; soil organic carbon and total nitrogen concentrations were improved through MT compared to CT. Grain yield was significantly associated with NDVI, grain N-content, and N-uptake. Therefore, a CT plus haricot bean-maize rotation system with the addition of solely 92 kg N ha−1 and integrated 46 kg N ha−1 + 10 t compost ha−1 could be recommended for Hawassa Zuria (Cambisols) and Meskan (Chernozem) districts, respectively. However, in order to ensure sustainable maize production in the investigated areas, an integrated N treatment with MT and a rotation system may be recommended, which could improve soil properties.

Thorn J.P., Biancardi Aleu R., Wijesinghe A., Mdongwe M., Marchant R.A., Shackleton S.

• Developed eight-part framework of barriers distinct to peri-urban UGI implementation. • 832 households surveyed and 118 key informants interviewed. • 18 forms of green infrastructure and 47 derived ecosystem services determined. • Scale up co-designed restoration, monitoring, coordination, and cost-benefit analyses. • Limit ecosystem disservices by managing waste, faecal contamination, and crime. Despite a growing recognition of the importance of designing, rehabilitating, and maintaining green infrastructure to provide essential ecosystem services and adapt to climate change, many decision makers in sub-Saharan Africa continue to favour engineered solutions and short term economic growth at the expense of natural landscapes and longer term sustainability agendas. Existing green infrastructure is typically maintained in more affluent suburbs, inadvertently perpetuating historic inequalities. This is in part because there remains a lack of fine-grained, comparative evidence on the barriers and enablers to mainstreaming green infrastructure in peri-urban areas. Here, we developed an analytical framework based on a review of 155 studies, screened to include 29 studies in 24 countries. Results suggest eight overarching categories of interconnected barriers to green infrastructure in peri-urban areas. Using a combinatorial mixed method approach, we then surveyed households in nine settlements in drought-prone Windhoek (n=330) and seven settlements in flood-prone Dar es Salaam (n=502) and conducted key informant interviews (n=118). Peri-urban residents in Windhoek and Dar es Salaam indicated 18 forms of green infrastructure and 47 derived ecosystem services. The most frequently reported barriers were financial (40.8%), legal and institutional barriers (35.8%) followed by land use change and spatial trade-offs (33%) and finally ecosystem disservices (30.6%). The most significant barriers in Dar es Salaam were legal and institutional (22.7%) and in Windhoek were land use change and spatial trade-offs (24.4%). At the household level, the principal barrier was financial; at community and municipal levels the main barriers were related to design, performance, and maintenance; while at the national level, the main barriers were legal and institutional. Embracing institutional cultures of adaptive policymaking, equitable partnerships, co-designing futures, integrated landscape management and experimental innovation have potential to scale long term maintenance for urban green infrastructure and foster agency, creativity and more transformative relationships and outcomes.

Smith A.C., Tasnim T., Irfanullah H.M., Turner B., Chausson A., Seddon N.

Many lower-income countries are highly vulnerable to the impacts of natural disasters and climate change, due to their geographical location and high levels of poverty. In response, they are developing climate action plans that also support their sustainable development goals, but conventional adaptation approaches such as hard flood defenses can be expensive and unsustainable. Nature-based solutions (NbS) could provide cost-effective options to address these challenges but policymakers lack evidence on their effectiveness. To address this knowledge gap, we focused on Bangladesh, which is exceptionally vulnerable to cyclones, relative sea-level rise, saline intrusion, floods, landslides, heat waves and droughts, exacerbated by environmental degradation. NbS have been implemented in Bangladesh, but there is no synthesis of the outcomes in a form accessible to policymakers. We therefore conducted a systematic review on the effectiveness of NbS for addressing climate and natural hazards, and the outcomes for other sustainable development goals. Research encompasses protection, restoration and participatory management of mangroves, terrestrial forests and wetlands, as well as conservation agriculture and agro-forestry, but there is an evidence gap for urban green infrastructure. There is robust evidence that, if well-designed, these NbS can be effective in reducing exposure to natural disasters, adapting to climate change and reducing greenhouse gas emissions while empowering marginalized groups, reducing poverty, supporting local economies and enhancing biodiversity. However, we found short-term trade-offs with local needs, e.g. through over-harvesting and conversion of ecosystems to aquaculture or agriculture. To maximize NbS benefits while managing trade-offs, we identified four enabling factors: support for NbS in government policies; participatory delivery involving all stakeholders; strong and transparent governance; and provision of secure finance and land tenure, in line with international guidelines. More systematic monitoring of NbS project outcomes is also needed. Bangladesh has an opportunity to lead the way in showing how high quality NbS can be deployed at landscape scale to tackle sustainable development challenges in low to middle income countries, supporting a Green Economic Recovery. Our evidence base highlights the value of protecting irreplaceable natural assets such as mangroves, terrestrial forests and wetlands, and the non-market benefits they deliver, in national planning policies.

Adeyemi N.O., Atayese M.O., Sakariyawo O.S., Azeez J.O.

KAYAMA M., ABEBE B., BIRHANE E.

In northern Ethiopia, considerable enrichment planting is essential to enhance the regeneration of dry forests. However, planted seedlings suffer high levels of mortality in arid climates. Biochar can enhance seedling survival and growth. Therefore, this study aimed to determine the effect of biochar (derived from Vachellia etbaica) on the survival of V. etbaica and Faidherbia albida seedlings. We planted V. etbaica and F. albida into soil treated with 1 kg of biochar per seedling and into soil without biochar (control) using a randomized complete block design. We analyzed the soil nutrients, plant growth, and plant elements. The application of biochar did not increase the nutrient levels in the soil. However, the total dry mass of V. etbaica and F. albida increased following biochar application. Moreover, the total contents of several nutrients were higher in the leaves of biochar-treated V. etbaica and leaves and roots of biochar-treated F. albida than in the controls. These results suggest that biochar can alter the chemical properties of soil, resulting in the accelerated uptake of nutrients. In conclusion, the application of biochar enhances the uptake of nutrients, thereby enhancing the growth of V. etbaica and F. albida.

Koutika L., Koné A.W., Kaonga M.

Okello C., Githiora Y.W., Sithole S., Owuor M.A.