Many environmental factors constrain the production of major food crops in Sub-Saharan Africa and South Asia. At the same time, these food production systems themselves have a range of negative impacts on the environment. In this paper we review the published literature and assess the depth of recent research (since 2000) on crop x environment interactions for rice, maize, sorghum/millets, sweetpotato/yam and cassava in these two regions. We summarize current understandings of the environmental impacts of crop production systems prior to crop production, during production and post-production, and emphasize how those initial environmental impacts become new and more severe environmental constraints to crop yields. Pre-production environmental interactions relate to agricultural expansion or intensification, and include soil degradation and erosion, the loss of wild biodiversity, loss of food crop genetic diversity and climate change. Those during crop production include soil nutrient depletion, water depletion, soil and water contamination, and pest resistance/outbreaks and the emergence of new pests and diseases. Post-harvest environmental interactions relate to the effects of crop residue disposal, as well as crop storage and processing. We find the depth of recent publications on environmental impacts is very uneven across crops and regions. Most information is available for rice in South Asia and maize in Sub-Saharan Africa where these crops are widely grown and have large environmental impacts, often relating to soil nutrient and water management. Relatively few new studies have been reported for sorghum/millets, sweetpotato/yam or cassava, despite their importance for food security on large areas of marginal farmland in Sub-Saharan Africa – however, there is mounting evidence that even these low-input crops, once thought to be environmentally benign, are contributing to cycles of environmental degradation that threaten current and future food production. A concluding overview of the emerging range of published good practices for smallholder farmers highlights many opportunities to better manage crop x environment interactions and reduce environmental impacts from these crops in developing countries.

Species of the genus Eucalyptus (common name eucalyptus) are widely planted all across Ethiopia—including on large areas of land previously allocated to food production. In recent decades eucalyptus has also increasingly been planted on lands around and within “church forests,” sacred groves of old-aged Afromontane trees surrounding Ethiopian Orthodox Tewahido churches. These revered holy sites have long been recognized for their cultural values and also for their ecosystem services—including their potential to support species conservation and restoration, as church forests are some of the only remaining sanctuaries for many of Ethiopia’s indigenous and endemic plant and animal populations. Ethiopian Orthodox church communities have a long history of planting and nurturing indigenous tree seedlings to sustain church forest groves. However, due to the fast-growing nature of eucalyptuscombined with its widely recognized socio-economic benefits (as fuelwood, charcoal, construction wood, etc.), this introduced species has been widely plantedaround church forests—in some cases even replacing native tree species within church forests themselves. In many developing country contexts the introduction of exotic eucalyptus has been shown to have ecological impacts ranging from soil nutrient depletion, to lowering water tables, to allelopathic effects. In this study, we collected soil samples from indigenous forest fragments (church forests), adjacent eucalyptus plantations, and surrounding agricultural land to examine how eucalyptus plantations in Ethiopian Orthodox church communitiesmight impact soil quality relative to alternative land uses. Soil properties, including organic matter, pH, total nitrogen, and total phosphorus were measured in samples across 20 church forest sites in South Gondar, East Gojjam, West Gojjam, Awi, and Bahir Dar Liyu zones in the Amhara Region of the northern Ethiopian Highlands. Findings indicate that although soil in eucalyptus stands is more acidic and has lower organic matter and nutrient levels than nearby church forests, eucalyptusplantations also exhibit consistently higher organic matter and nutrient levels when compared to adjacent agricultural land. These findings suggest that eucalyptus planting could potentially benefit soil fertility on land that has been degraded by subsistence agriculture.

Some of the only Afromontane forest in northern Ethiopia today is on lands managed by followers of the Ethiopian Orthodox Church, where for centuries priests and communities have conserved forest groves around church buildings. The ecological value of the thousands of church forests in Ethiopia has been widely acknowledged, but little is known about the diverse local institutions that govern these resources, or how such institutions might be changing in response to Ethiopia's rapid recent economic development. This study uses a unique panel survey to explore changes in community perspectives on the social and ecological roles of church forests, and rules governing church forest use, in four Orthodox communities over time. Our sample consists of 122 household surveys conducted in 2002 and a further 122 surveys from 2014, with 71 households interviewed in both periods. We find that reported uses of church forests vary across forests and 356 Travis William Reynolds et al. over time, with larger forests more likely to be used for extractive purposes such as firewood and construction timber, while smaller forests have become more restricted to renewable or non-extractive uses such as natural medicines, honey, and prayer. Results of logistic regression suggest church followers' support for preserving church forests increases with age and access to alternative sources of firewood-including exotic Eucalyptus spp. plantations which are increasingly widespread in northern Ethiopia. We also observe a shift since 2002 away from an expectation that church followers themselves hold responsibility for rule enforcement in church forests to a perceived sharing of responsibility by church authorities (i.e. priests) and government (i.e. police) in 2014. Together the progressive introduction of exotic tree species in church forests combined with the erosion of religious norms surrounding local forest governance may threaten the integrity and diversity of these unique social-ecological systems.

Crop production is a major livelihood activity of smallholders in Ethiopia. However, it is often characterized by low performance. In an effort to improve crop production, a series of agricultural extension programs have been running in Ethiopia since the 1950s. Nevertheless, the performance of agriculture is still low. In this study, it is argued that the limited attention given to cropland allocation methodologies is one of the major causes of low performance of crop production and increased environmental degradation. This study used linear programming to examine the role and impacts of cropland allocation methods on performance of crop production. The data for this study was drawn from household survey of 75 randomly selected households combined with focus-grouped discussion, key informant interview, and secondary data. In the current conventional cropland allocation, households were not able to meet their household consumption. The average profitability of farms under current practice was found significantly below than estimated optimal level of profit that could be realized using linear programming. In addition, it uncovered that low performance of crop production (in terms of meeting household consumption demand and profitability) is the primary cause that limited the effort of households to participate in environmental and natural resource management. This study suggests the use of linear programming-based cropland allocation to enhance the profit performance of smallholder crop production, meeting household consumption requirement, and thereby promote sustainable utilization of natural and environmental resources.