Organic agriculture (OA) is a holistic production management system which promotes and enhances agro-ecosystem health, including biodiversity and biological cycles. It emphasizes the use of management practices in preference to the use of off-farm inputs. This is accomplished by using cultural, biological and mechanical methods, as opposed to using synthetic materials (FAO, 2009c). A specific feature of OA is that its production practices are defined by organic standards which ban the use of synthetic inputs and GMOs and, hence, has to maximize the use of ecosystem services in order to compensate for the input ban. OA is no longer a phenomenon in developed countries only, as it is commercially practiced in 187 countries, representing 72.3 million hectares (Willer and Kilcher, 2021).

• Diversity. As organic systems rely on ecosystem services to improve soil fertility, biological pest control and nutrient and energy balances in order to compensate for the prohibition on synthetic input use, they usually feature enhanced floral and faunal diversity as compared to conventional and integrated pest management systems (Maeder et al., 2002; Pacini et al., 2003).

• Coherence. The objective of organic management is to establish, to the extent possible, closed energy and nutrient cycles (e.g. biomass recycling). This coherence between natural and human processes is further extended in biodynamic agriculture, the earliest among the initiatives from which organic farming evolved since 1920s, currently covering more than 140 000 hectares in 47 countries (Demeter, 2011). A specific feature of biodynamic agriculture, inspired by Rudolf Steiner (1861-1925) is the regeneration of the forces that work through the soil to the plant by using compost and spray preparations from naturally fermented organic substances in minute doses to soils and crops. By contrast, in some cases, such as horticulture in California, USA, enforcing of minimal compliance with organic standards has led to a process of intensification and specialization that disrupts the farm nutrient cycles when the cropping systems must heavily rely on imports of organic inputs (e.g. replacement of farm-produced animal and green manure with external organic fertilizer). For smallscale farmers in developing countries faced with lack of capital and low product prices, closing the nutrient cycle is a necessity rather than an optional commitment (Zundel and Kilcher, 2007). Within-farm, vertical integration gives rise to opportunities to keep the added value of high quality products in the farm budget that increase on-farm job opportunities and enhance farm socio-economic coherence.

• Connectedness. Organic farms usually maintain hedgerows, vegetative buffer strips, riparian corridors, buffer zones and other landscape features that provide shelter to predators, pollinators and other biodiversity beneficial to agricultural production. Such habitat enhancement practices reduce landscape fragmentation and the absence of pesticides in the agro-ecosystem provides for biodiversity conservation, in addition to preserving human health (Scialabba and Williamson, 2004). In several settings, it has been noted that increased control over resources (labour power, production system) develops self-awareness and collective self-help, which lead to overcoming marginalization through participatory initiatives.

• Efficiency. With the current level of agroecological knowledge, average organic productivity (yield per hectare for ten plant and animal food categories recognised by FAO) ranges from -10 percent, as compared to high external inputs systems, to +80 percent in low external input conditions in developing countries (Badgely et al., 2007). Increased biomass in organically managed soils decreases irrigation water needs, but more land is usually required due to lower productivity, as compared to high external input systems in developed countries. A 21 year study by the FiBL Institute in Switzerland (DOK trials) compared the performance of biodynamic, organic and two conventional systems and found that nutrient input in the biodynamic and organic systems was 34 to 51 percent lower than in the conventional systems, but crop yield was only 20 percent lower on average, indicating more efficient production. In regard to soil aggregate stability, soil pH, humus formation, soil calcium, microbial biomass, and faunal biomass, the biodynamic system was superior even to the organic system (Maeder et al., 2002). Generally, less energy is needed due to foregoing synthetic inputs use – from 45 to 67 percent, as reported by Pimentel (2006) and Williams et al. (2006), respectively. However, this benefit is neutralized in industrial farms that substitute labour with mechanization. Overall, organic systems have demonstrated to compensate for GHG emissions through enhanced soil carbon sequestration and can often be carbon neutral (Scialabba and Müller-Lindenlauf, 2010). Labour costs in organic farms are usually higher, due either to higher wage costs or labour needs. However, despite higher labour inputs, production costs are lower in both developed and developing countries, rendering organic farms economically more profitable than conventional, often even if extra prices for organic products are not obtained on food markets (Nemes, 2009).

• Resilience. By managing biodiversity in time (rotations) and space (mixed cropping and mixed crop-livestock systems), organic farmers also enhance diversity of cultivated and wild species, with positive effects in terms of resilience to climate variability and market price fluctuations of commodities and inputs.

Capacity for a green economy. The challenge of OA is to intensify production while maintaining ecosystem integrity. While in developing countries, organic management is an option for ecological intensification, in industrial contexts, it becomes an extensification strategy. The issue is whether enough surpluses could be produced on a global basis to meet population demands and at which price, given the fact that currently organic product prices are higher on average. The issue of land availability for extensification might be of concern in some areas, while in others, organic agriculture might relocalize food systems where food is most needed, such as market-marginalized areas where hunger prevails (e.g. areas of sub-Saharan Africa). Provided that organic farmers will be able to demonstrate and certify the environmental benefits they produce, in industrialized areas, there will be need to fund the transition phase and compensate for decreased yields until soil fertility is restored, while in developing countries, there will be need for promotion of agroecological knowledge generation and dissemination. Despite increasing trends of adoption, concerns are raised on the actual capacity of organic farming to meet food needs on global scale. The principal objections to the proposition that organic agriculture can contribute significantly to the global food supply are low yields and insufficient quantities of organically acceptable fertilizers. Badgely et al. (2007) modelled the global food supply that could be grown organically on the current agricultural land base, based on FAO data on ten plant and animal food categories. Model estimates indicate that organic methods could produce enough food on a global per capita basis to sustain the current human population, and potentially an even larger population, without increasing the agricultural land base. The authors also evaluated the amount of nitrogen potentially available from fixation by leguminous cover crops used as fertilizer in organic farming; data from temperate and tropical agro-ecosystems suggest that leguminous cover crops could fix enough nitrogen to replace the amount of synthetic fertilizer currently in use. It can be concluded that the OA potential for greening agriculture is considerable, especially under scenarios of ecological intensification in developing countries and in those areas faced with degraded soils or lack of capital and low product prices.