Prioritizing farm management interventions to improve climate change adaptation and mitigation outcomes—a case study for banana plantations

Intervening into agricultural systems necessarily includes risks, uncertainties, and ultimately unknown outcomes. Decision analysis embraces uncertainty through an interdisciplinary approach that involves relevant stakeholders in evaluating complex decisions. We applied decision analysis approaches to prioritize 21 farm management interventions, which could be considered in certification schemes for banana production. We estimated their contribution to climate change adaptation and mitigation as well as ecological outcomes. We used a general model that estimated the impacts of each intervention on adaptation (benefits minus costs), mitigation (global warming potential), ecological parameters (e.g., biodiversity and water and soil quality), and farming aspects (e.g., yield, implementation costs and production risks). We used expert and documented knowledge and presented uncertainties in the form of 90% confidence intervals to feed the model and forecast the changes in system outcomes caused by each intervention compared to a baseline scenario without the measure. By iterating the model function 10,000 times, we obtained probability distributions for each of the outcomes and farm management interventions. Our results suggest that interventions associated with nutrient management (e.g., composting and nutrient management plan) positively affect climate change adaptation, mitigation, and ecological aspects. Measures with no direct yield benefits (e.g., plastic reduction) correlate negatively with adaptation but have positive impacts on ecology. Creating buffer zones and converting low-productivity farmland (incl. unused land) also have positive ecological and adaptation outcomes. Decision analysis can help in prioritizing farm management interventions, which may vary considerably in their relationship with the expected outcomes. Additional work may be required to elaborate a comprehensive assessment of the underlying aspects modulating the impacts of a given measure on the evaluated outcome. Our analysis provides insights on the most promising interventions for banana plantations and may help practitioners and researchers in focusing further studies. Supplementary Information The online version contains supplementary material available at 10.1007/s13593-022-00809-0.


Introduction
In the following document, we offer supplementary information on the materials and methods as well as the results of the work 'Prioritizing certification interventions to improve climate change adaptation and mitigation outcomes -a case study for banana plantations' by Fernandez et al. (2022). The work is published in the journal Agronomy for Sustainable Development under the doi: 10.1007/s13593-022-00809-0. As mentioned in the main text, all scripts and analyses are available in a public repository hosted at: https://github.com/CWWhitney/Certification_ Prioritization.

Annex 1: List of measures
After consultation with the experts and the literature we reduced the overall list of certification options to 21 interventions, categorized into 5 groups. For each of these, the growers/producers/producer groups would be responsible for implementation. The descriptions for each measure are provided below. We also provide the sources of information for model inputs for each measure. Sources, where mentioned, were used in addition to experts and our own estimates.

Buffer zone
Buffer zone certification measures would require that banana plantations include vegetative buffers at the edges of cropped fields. In this measure growers are required to maintain existing riparian buffer zones around aquatic ecosystems, bodies of water and watershed recharge areas and between production and areas of high conservation value, either protected or not. Pesticides, hazardous chemicals and fertilizers are not applied. The buffer zones could be covered with grass, shrubs, trees or a mix of vegetation (McKergow et al. 2004). Buffer zones provide mainly ecological benefits such as preventing chemical runoff and drift (McKergow et al. 2004) and act as biodiversity corridors (Ducros and Joyce 2003). The implementation of buffer zones may be costly and also have trade-offs with the banana yield (area sacrificed to buffer zones). The practice of agroforestry in the buffer areas may provide a successful management strategy for both environmental and economic benefits (Rahman et al. 2014).
Input data (i.e. 90% confidence intervals) for all variables associated with this measure were obtained from various sources including Collentine et al. (2015), Ducros and Joyce (2003), Melo and Wolf (2005), McVittie et al. (2015), Muscutt et al. (1993) and Zhu, Yang, and Zhang (2021). We updated these values using knowledge from experts as well as our own judgement when we considered the intervals to be too narrow.

Conversion of low-productivity farmland (incl. unused land)
In this certification measure, banana growers would convert unproductive sites into conservation areas where viable. They would develop a map that includes natural ecosystems and agroforestry canopy cover or border plantings with estimated vegetation coverage and estimated percentage of native species composition and progressively increase or restore native vegetation adjacent to aquatic ecosystems, farmed areas of marginal productivity and around housing and infrastructure. This could include live fences, shade trees and permanent agroforestry systems. Our models assumed that the unused land areas are likely to be a rather small portion of the total plantation land. There will be economic benefits from other harvest (e.g. from the agroforestry system) and ecological benefits such as increasing farm biodiversity.
Input data (i.e. 90% confidence intervals) for all variables associated with this measure were mainly obtained from Vallejo-Chaverri et al. (2018). We updated these values using knowledge from experts as well as our own judgement when we considered the intervals to be too narrow.

Energy use plan
With this measure banana producers would be required to keep track of the energy consumption and explore the options to reduce environmental impacts and costs associated with the non-renewable energy use. Within the banana production system, energy sources such as fossil fuel and electricity are mainly used in packing plants (e.g. lighting, water supply and conveyor belt) and to extract water for irrigation and to operate within-plantation transportation systems.
Input data (i.e. 90% confidence intervals) for all variables associated with this measure were obtained from various sources including Păunescu and Blid (2016) and Vallejo-Chaverri et al. (2018). We updated these values using knowledge from experts as well as our own judgement when we considered the intervals to be too narrow.

Energy equipment
With this measure banana growers would select and invest in energy-efficient equipment where possible and maintain it for optimum energy consumption. This measure could help to reduce the energy consumption in the production system and lower energy costs. The measure could also reduce overall emissions due to lower fossil fuel combustion.
Input data (i.e. 90% confidence intervals) for all variables associated with this measure were obtained from various sources including Akcaoz (2011) andLin, Lin, andPeng (2019). We updated these values using knowledge from experts as well as our own judgement when we considered the intervals to be too narrow.

Solar energy
This certification measure requires that producers reduce the use of non-renewable energies and offset or replace them with solar energy. According to experts, solar may already be feasible (cost effective) in some banana plantations in Latin America but is not yet a widely available option.

Other renewable energy sources
This certification measure requires that producers reduce the use of non-renewable energies and offset or replace them with biomass energy. In this certification measure organic wastes from banana production are used for generating power on the plantation. The biomass used for energy generation can be costly and resource intensive (water, soil, synthesized inputs, energy etc.). Efficient technologies to make this practicable may not be widely available (i.e. cost effectiveness may be an issue).
Input data (i.e. 90% confidence intervals) for all variables associated with this measure were mainly obtained from Tock et al. (2010). We updated these values using knowledge from experts as well as our own judgement when we considered the intervals to be too narrow.

Wastewater reuse
Packing bananas, which uses a lot of water, is done daily during the harvest season. This certification measure requires that producers collect and re-use this water for irrigation. However, the wastewater from packing plants is prone to risks of salinity, phytotoxicity and other contaminants which can affect banana plants, soil and water ecosystems. In addition, wastewater from banana processing contains latexes that might impact soils and the banana fields. Proper treatment before using for irrigation is needed. The measure may reduce the risk of water shortage for irrigation but may incur additional costs for water treatment.
Input data (i.e. 90% confidence intervals) for all variables associated with this measure were obtained from various sources including Russo and Hernández (1995) and van Asten, Fermont, and Taulya (2011). We updated these values using knowledge from experts as well as our own judgement when we considered the intervals to be too narrow.

Water reservoir
This certification measure requires the construction of reservoirs to collect rainwater and store water for dry periods. This can help to reduce risks of water shortage for production and at the same time reduce the impact of high rain intensity (i.e. surface runoff and waterlogging) during heavy rain events. The water storage also reduces ground water withdrawal, which may have a positive impact on aquatic ecosystems. The reservoirs can be trenches that are dug along plantation contours to keep water around the cultivated areas. The costs involved could be mainly labor and basic construction materials for digging and maintaining the trenches. The trade-off could be less land available for banana production.
Input data (i.e. 90% confidence intervals) for all variables associated with this measure were mainly obtained from Mugerwa (2007) and http://www.agritech.tnau.ac.in/expert_system/banana/irrigationmanagement.html#5. We updated these values using knowledge from experts as well as our own judgement when we considered the intervals to be too narrow.

Anti-evapotranspiration spray
This certification measure requires the use of organic anti-evapotranspiration substances to reduce water evapotranspiration and increase water use efficiency of bananas. The use of anti-transpirant in combination with appropriate irrigated regimes can reduce the total amount of irrigated water during the growing season (El-Kader 2006). However, in high rainfall regions the use of organic foliar spray against evapotranspiration may be less relevant than in low rainfall regions. It could suppress banana growth and development by reducing photosynthesis. Methods such as mulching and ground cover may be more effective in managing evaporation from the soil surface.
Input data (i.e. 90% confidence intervals) for all variables associated with this measure were mainly obtained from El-Kader (2006) and Gawad (2014). We updated these values using knowledge from experts as well as our own judgement when we considered the intervals to be too narrow.

Irrigation methods
With this certification measure banana growers would improve irrigation methods. Improved irrigation can increase both water-use efficiency and yield. According to experts, under canopy single-and series-sprinkler irrigation systems are the most common irrigation techniques for large scale banana production. Experts agree that this is a highly efficient method. Furrow irrigation, flood irrigation are common but are considered low efficiency. Drip irrigation is also applied on some plantations and could perform well in semi-arid areas where availability of water is low.
Input data (i.e. 90% confidence intervals) for all variables associated with this measure were obtained from various sources including de Oliveira et al. (2009), N. Panigrahi et al. (2021, Pawar, Dingre, and Bhoi (2017) and Pramanik and Patra (2016). We updated these values using knowledge from experts as well as our own judgement when we considered the intervals to be too narrow.

Irrigation scheduling
Irrigation scheduling requires the calculation of crop water requirement, crop water demand at different growth stages, soil moisture, evapotranspiration rate, among other water use factors (P. Panigrahi et al. 2019). Certification requirements for irrigation scheduling could provide synchrony of water needed and the quantity of water supplied which, in turn, could enhance irrigation efficiency and reduce water waste (Israeli, Hagin, and Katz 1985;N. Panigrahi et al. 2021).
Input data (i.e. 90% confidence intervals) for all variables associated with this measure were obtained from various sources including de Oliveira et al. (2009), Minhas et al. (2020) and N. Panigrahi et al. (2021). We updated these values using knowledge from experts as well as our own judgement when we considered the intervals to be too narrow.

Drainage management
With this certification measure managers would be required to design drainage systems based on the biophysical characteristics of the plantation such as soil type and structure, water system, slope and ground cover to improve farm drainage capacity. They would also identify erosion prone areas, areas with high risk of flooding and those with poor drainage conditions. According to experts, open systems with water channels along the banana plots are common. These perform sufficiently to avoid waterlogging. A good drainage system will help to reduce the risk of waterlogging which may be critical in high rainfall regions.
Input data (i.e. 90% confidence intervals) for all variables associated with this measure were mainly obtained from Vallejo-Chaverri et al. (2018). We updated these values using knowledge from experts as well as our own judgement when we considered the intervals to be too narrow.

Composting
With this certification measure banana growers would make compost from farm plant residues and use compost and green fertilizers as a source of plant nutrients. This may reduce the cost for chemical fertilizers. Farmers can combine compost with other sources of nutrients, which has been proved to contribute to increase the yield of crops (Bekunda and Woomer 1996;Ouédraogo 2001). Application of compost can increase soil fertility and microbial activities as well as enhance the water holding capacity of sandy soil. Composting requires low cost of inputs such as plant materials, animal manures that can be found around the plantation. However, the practice may require more labor in the process of making compost.
Input data (i.e. 90% confidence intervals) for all variables associated with this measure were obtained from various sources including Kukulies et al. (2014), Meya et al. (2020) and Wairegi and Asten (2010). We updated these values using knowledge from experts as well as our own judgement when we considered the intervals to be too narrow.

Nutrient management
This measure would require farmers to apply nutrient management practices based on assessments of crop needs, regular monitoring of soil fertility and crop nutrient status, or recommendations from local agronomic experts. Regular soil tests and leaf tests including macro-and micro-nutrients and organic matter would be carried out frequently. Management practices such as choosing appropriate nutrient doses, forms and sources as well as deciding on the right time and method of application may help farmers to reduce chemical fertilizer used without compromising the yield (Israeli, Hagin, and Katz 1985;Keshavan, Kavino, and Ponnuswami 2011;Lobell 2007;Wairegi and Asten 2010). The proper management of fertilizer application, especially nitrogen, could mitigate greenhouse gas (i.e. nitrous oxide -N2O and nitric oxide -NO) emission (Masters 2019;Rowlings et al. 2013;Veldkamp and Keller 1997). The synchronization of fertilizer application and crop demand could minimize chemical residues in drinking water and aquatic ecosystems (Henriques et al. 1997;Stover 1986;Svensson et al. 2018).

Integrated Pest Management (IPM)
This measure requires that banana growers to develop an integrated pest management (IPM) plan and follow regulations on sprays of pesticides. They would implement various IPM activities that could reduce the incidence and intensity of pest attacks, and thereby reduce the need for chemical intervention. Growers would also take part in training on integrated pest management including monitoring of pests and diseases, alternative ways to control pests and diseases, preventive measures against pests and diseases, measures to avoid buildup of pest and disease resistance to pesticides. They keep a list of the pesticides with names of active ingredients, crops on which the pesticides were used and the targeted pests. The implementation could help to reduce chemicals used which will decrease production costs and emissions from chemical manufacturing, as well as avoid economic losses due to pest incidence. The production systems with reduced pesticide application could also have less negative impacts on human and wildlife (e.g. acute toxicity) (Henriques et al. 1997) and local biodiversity.
Input data (i.e. 90% confidence intervals) for all variables associated with this measure were obtained from various sources including Barraza et al. (2011), Barraza et al. (2020), Blazy et al. (2009), Castillo et al. (2006, Chaves, Shea, and Cope (2007) and Côte et al. (2009). We updated these values using knowledge from experts as well as our own judgement when we considered the intervals to be too narrow.

Reincorporate crop residues
With this certification measure banana growers would be required to use organic waste from their farm production for mulching. The banana residue would be retained in the field. This could also contribute to reducing organic waste from the plantation and increase soil cover to prevent runoff. Mulching may also to increase banana yields as it was the case with mulching, in combination with mineral fertilizers, in banana plantations in Uganda (Wairegi and Asten 2010).
Input data (i.e. 90% confidence intervals) for all variables associated with this measure were mainly obtained from Tursun et al. (2018). We updated these values using knowledge from experts as well as our own judgement when we considered the intervals to be too narrow.

Cover crops
With this measure banana farmers would plant cover crops to avoid bare soils, reduce erosion and weed infestation. The ground cover could reduce nutrient losses from leaching (cover crop as catch crop) and mitigate greenhouse gas emission (Abdalla et al. 2019;Lavigne et al. 2012). However, planting cover crops incurs costs for establishing and maintaining the vegetation. There is also a chance that cover crops will compete for resources with cash crops which may affect the yield (Abdalla et al. 2019;Lavigne et al. 2012).
Input data (i.e. 90% confidence intervals) for all variables associated with this measure were obtained from various sources including Abdalla et al. (2019), Blazy et al. (2009), Johns (1994, Kukulies et al. (2014), Quaresma, Oliveira, and Silva (2017), Tursun et al. (2018) and Vallejo-Chaverri et al. (2018). We updated these values using knowledge from experts as well as our own judgement when we considered the intervals to be too narrow.

Recycling plastic
This certification measure would require banana farmers to collect plastic used in the farm and send it to plastic recyclers. The practice may incur small labor cost for gathering and compacting used plastic materials. Plastic recycling will mainly have ecological benefits for both terrestrial and aquatic ecosystems.
Input data (i.e. 90% confidence intervals) for all variables associated with this measure were mainly obtained from Russo and Hernández (1995) and Svanes and Aronsson (2013). We updated these values using knowledge from experts as well as our own judgement when we considered the intervals to be too narrow.

Waste disposal plan
The commercial banana plantations face a challenge managing their waste, particularly plastic waste used to protect the plant during its growing period and solid waste used in the packing plant for post-harvest (Russo and Hernández 1995). The banana producer therefore needs a concrete management plan for proper disposal of those undesired by-products. This certification measure would require farmers to calculate and record types and amounts of waste from different units of the production process for identifying the potential measures for waste treatments.
Input data (i.e. 90% confidence intervals) for all variables associated with this measure were obtained from various sources including Melo and Wolf (2005), Russo and Hernández (1995) and Vallejo-Chaverri et al. (2018). We updated these values using knowledge from experts as well as our own judgement when we considered the intervals to be too narrow.

Plastic reduction
This certification measure would require banana growers to reduce plastic use by using a continuous polyethylene tube instead of the standard pre-cut impregnated plastic bags to protect banana bunches. It is possible to minimize plastic use by fitting the tube to the exact length of the bunches. This method can increase labor costs when using the replacement plastics. However, it also helps reduce plastics purchased, thus reducing production costs, plastics produced as well as environmental impacts on land, water bodies and human habitats.
Input data (i.e. 90% confidence intervals) for all variables associated with this measure were mainly obtained from Russo and Hernández (1995). We updated these values using knowledge from experts as well as our own judgement when we considered the intervals to be too narrow.

Plastic re-use
This certification measure would require banana farmers to re-use plastics, such as the protecting bags and plastic twine for holding up banana plants. The measure incurs an increased labor cost to collect and treat the bags again before reuse. Plastic reuse may reduce production costs and reduce plastic waste, which will contribute to both economic and environmental benefits.
Input data (i.e. 90% confidence intervals) for all variables associated with this measure were mainly obtained from Russo and Hernández (1995). We updated these values using knowledge from experts as well as our own judgement when we considered the intervals to be too narrow. We generated a table of confidence estimates (90%) for use in the decision model. Most variable values are described as a percentage difference from a baseline (in decimals). Others, such as coefficient of variation (coeff. Variation) and ecological values are described as integers.

Annex 2: Model function
We developed a general function that estimates costs, benefits, risk reduction and risk increase, adaptation and mitigation to climate change, and the ecological impact of any certification measure (see certification_impact.R in https://github.com/CWWhitney/Certification_Prioritization). This allowed us to obtain a common output structure independent of the certification measure evaluated. The simulation was run to represent 10 years of a typical banana production system.
Later, we applied this function to all certification measures using the specific information we gathered for each.The ultimate aim was to get a list of the measures that influence adaptation, mitigation and environmental outcomes (see return() list at the end of the certification_measures_function.R in https://github.com/CWWhitney/ Certification_Prioritization).
After coding the impact pathways we performed a Monte Carlo simulation with the mcSimulation() function from decisionSupport (Luedeling et al. 2022). This function generates a distribution representing the desired outputs (see return() function above) by calculating random draws in our defined certification_measures_function(). Inside this simulation we use a generalized function called certification_impact() to establish the possible impacts of each measure.

Supplementary figures Figure S1
In Fig. S1 we show the detailed impact pathway representing the potential underlying relationships between the certification measures and the farm productivity (i.e. adaptation aspect). For the measures in the Energy group, we estimated a decline in energy consumption as well as a positive impact on implementation costs. The relationships within the remaining groups were more complex. For instance, our model suggests salinity as a potential driver for banana yields in case wastewater is used for irrigation (Fig. S1). Similar intermediate variables affecting the productivity of the farm can be identified in our impact pathway.

Figure S2
In Fig. S2 we show the detailed impact pathway representing the potential underlying relationships between the certification measures and global warming potential and ecological aspects. For global warming, we identified fossil fuel consumption as a driver of greenhouse gas emission (Fig. S2). In the case of ecological aspects, we identified a number of variables modulating the impact on the environment. Among them, soil salinity, water supply capacity, overland flow, organic matter and fertilizer and pesticide use could be key determinants for the measures' impacts in this regard (Fig. S2).

Annex 3: Expert survey
The Action Alliance for Sustainable Bananas (ABNB) pledged to intensify its activities in the field of climate change adaptation and mitigation in the banana sector. Various measures to adapt to climate change effects are widely in place, some are already adopted by innovators and some are yet to be tested. ABNB wants to utilize the expertise and knowledge of experts in the field of climate change adaptation and mitigation in order to evaluate, which measures -that are currently available to most farmers -are most effective, cost-effective and pose the fewest risks.
Using Decision Analysis tools, the qualitative expertise and knowledge will be channeled and analyzed -quantifying individual knowledge and for making it measurable. The goal is to receive a prioritized list of measures, which should guide not only plantation owners and farmers but also certification schemes.
This questionnaire is to consult with banana and climate change experts to understand more about the banana production system as well as the potential of climate change adaptation and mitigation measures.
Please note that the questions refer to commercial banana production in humid regions. If you have any relevant resources or feedback, please kindly share in your answer or email cory.whitney@unibonn.de

II. Irrigation and drainage
11. What are the main sources of water that banana production relies on? Choose all that apply.