Biological Crusts to Increase Soil Carbon Sequestration: New Challenges in a New Environment

Simple Summary Scientific knowledge should transcend the barriers between the laboratory and the field to act in the service of humanity. Considering the enormous potential that soil offers for organic carbon (SOC) sequestration for the mitigation of greenhouse gas (GHG) emissions, and considering the recognized ecological importance of biological soil crusts (biocrusts) to be applied in the soil-plant continuum, we propose three perspectives to apply biocrusts to sustainable agriculture. The major priority of research in the present day is to conserve the environment by reducing GHG emissions. A proposed solution by an expert panel from 195 countries meeting at COP 21 was to increase global SOC stocks by 0.4% year(-1) to compensate for GHG emissions, the '4 per 1000 ' agreement. In this context, the application of biocrusts is a promising framework with which to increase SOC and other soil functions in the soil-plant continuum. Despite the importance of biocrusts, their application to agriculture is limited due to: (1) competition with native microbiota, (2) difficulties in applying them on a large scale, (3) a lack of studies based on carbon (C) balance and suitable for model parameterization, and (4) a lack of studies evaluating the contribution of biocrust weathering to increase C sequestration. Considering these four challenges, we propose three perspectives for biocrust application: (1) natural microbiome engineering by a host plant, using biocrusts; (2) quantifying the contribution of biocrusts to C sequestration in soils; and (3) enhanced biocrust weathering to improve C sequestration. Thus, we focus this opinion article on new challenges by using the specialized microbiome of biocrusts to be applied in a new environment to counteract the negative effects of climate change.