Threats to soil and its biodiversity

Soils and their biodiversity are presently under threat owing to global changes such as excessive land exploitation, climate change, pollution, and invasions of new species. All ecosystems on Earth are currently suffering the impact of these environmental pressures. The fraction of arid to semiarid ecosystems on Earth is increasing due to desertification. Furthermore, anthropogenic (human-driven) activities have resulted in substantial changes in nitrogen and phosphorus fluxes, altering global nutrient cycles.

Threats to the soils of the UAE: The dry nature of desert soils makes them very fragile as the recovery from environmental pressures is particularly difficult. Wind erosion has been shown to be the major cause of degradation by drifting soil (causing dust storms and Nabkha dunes, an indicator of dryland degradation). Soil salinity is also becoming a threat to farms and coastal areas. Climate change, waterlogging, overgrazing and landfilling for urban development are other factors that have been threatening the soils of the UAE.

Climate change and soil biodiversity

Climate change influences soil biodiversity directly due to changes in temperature and moisture, and also indirectly due to alterations in resource supply from plants. Combined, these lead to changes in the physiology and growth of many soil organisms, in turn causing alterations in the composition of soil communities. As a consequence, new traits and life histories within soil communities will be selected which may drive aboveground ecosystems and evolutionary dynamics to be affected, including the emission of greenhouse gas and leaching of dissolved carbon and nutrients from the soil. The increased frequency of extreme climatic events (temperature and precipitation, for example) seen and further expected globally is likely to have large impacts on ecosystems and, particularly, soil biodiversity.

Soil and the Sustainable Development Goals

Relationship between the Sustainable Development Goals, soil and ecosystem-based approaches. From Keesstra et al (2018) Land (https://www.mdpi.com/2073-445X/7/4/133)

A major goal of soil biodiversity research is to integrate what is being learned into sustainable land management policies. These policies have an impact on soil fertility for food, feed and biomass production, the prevention of human disease, and the mitigation of climate change. More than half of the Sustainable Development Goals (SDGs) depend on appropriate soil preservation. This is relevant for food security (SDGs 2 and 6), food safety and human health (SDG 3), urban development (SDG 11), as well as SDGs 1, 6, 12, 13, 14 and 15 which are associated to poverty reduction, clean water, responsible production, land management, climate change and overall biodiversity preservation. More specifically, the SDG target 15.3 on land degradation neutrality commits that “by 2030 to combat desertification, restore degraded land and soil, including land affected by desertification, drought and floods, and strive to achieve a land degradation-neutral world” (United Nations General Assembly. Transforming our world: the 2030 Agenda for Sustainable Development. October 21, 2015).

Did you know? In stark contrast to wildfires which damage and degrade the soil due to the high temperatures, prescribed fires are less intense and, when administered adequately, can contribute to increased soil fertility, grassland recovery, the regeneration of particular plant species, and allows for forest biomass management. Interestingly, some microbes such as the fungus Neurospora crassa are amongst the first colonizers of the soil and dead wood after a forest fire because their heat-resistant sexual spores benefit from the degree of sterility provided by the fire and rely on the higher temperature to germinate.

Soil biodiversity, food security and nutrition

ICBA scientists in the field

The soil functions are the base of agricultural activities and, hence, assure food productivity. However, increasing evidence indicates that agricultural intensification affects soil biodiversity and that such changes may have a very significant impact on the future of food security. Changes in land use or agricultural management affect soil biodiversity through: aboveground biomass removal/returns, use of agrochemical inputs and mechanical soil disturbance. Increasing evidence suggests that organic or agro-ecological farming leads to positive effects and helps in mitigating the decline in soil biodiversity, while reducing the dependency on external inputs.

Food demand is increasing. In contrast, land use conversion and inadequate management practices threaten the availability and stability of food supplies. In this context, the biotic component of the soil plays essential roles in soil dynamics such as carbon/nutrient cycling, nutrient uptake by plants and soil organic matter formation. Furthermore, soil organisms, namely earthworms and termites contribute to soil formation and regeneration through bioturbation and soil structuration. Soil organisms also contribute to the control of plant, animal, and human pests and diseases, and have a vital responsibility in regulating the adaptive capacity of the soil to global changes. Thus, an integrated management of soil biodiversity offers the potential to increase agricultural productivity by making more efficient use of resources, reducing yield variability, production costs and economic risks for the farmers, ultimately contributing decisively to food security. A holistic approach to agricultural land management consists of managing soil ecosystems and their diversity in a way that favors multifunctionality, resilience and adaptive capacity of the soil against environmental changes. This enhances agricultural productivity, an efficient application of resources and results in stable food production. This holistic approach considers the complexity, complementarity and self-regulation of soil biota and plant-soil biota interactions. In practical terms, it implies working closely with farmers to increase understanding and knowledge sharing about soil biodiversity and its role in food security. The implementation of a holistic approach to soil biodiversity management requires the diversification of the entire agroecosystem, through practices such as crop livestock integration, agroforestry, intercropping and crop rotation.

To think about: Proper human nutrition depends on the availability and balance of different nutrients in the soil and the ability of plants to extract those nutrients. Thus, nutrient limitations in the soil can lead to nutritional deficiencies in the food produced.

What’s new for soil microbiology

Actually, very little is known about soil microbes, partially because they are so diverse, but also because most soil microbes cannot be cultivated in the laboratory. For the ones that can be grown in a laboratory setting, scientists have used traditional methods such as direction observation, counting and functional assays, including the measurement of specific enzymatic activities. However, soil microbiologists have recently been applying advanced molecular techniques to understand the diversity and function of soil microbes. This exciting field, called soil metagenomics, relies on a cultivation-independent technology that comprises the isolation of soil DNA, its sequencing, and the characterization of the microbial communities present in soil samples. This has allowed many new taxa to be discovered in the rhizosphere – the narrow region of soil or substrate that is directly influenced by root secretions and associated soil microorganisms known as the root microbiome. Similar approaches are being used to study the human gut microbiome, for example.

Flow diagram showing the main steps in the construction of a metagenomic DNA library from a soil sample. Soil DNA is recovered through separation of cells from soil particles followed by cell lysis and DNA recovery, or through direct lysis of cells contained within soil and recovery of DNA. Recovered soil DNA is fragmented and ligated into the linearized cloning vector of choice which might be a plasmid, cosmid, fosmid or BAC (bacterial artificial chromosome). Following the introduction of the recombinant vectors into a suitable bacterial cloning host, screening strategies can be designed to identify those clones which might contain new and useful genes. Daniel (2005) Nature Reviews Microbiology (https://www.nature.com/articles/nrmicro1160)

Careers in Soil Science

Photos from ICBA

Despite the fact that they are the terrestrial surface we live on and that they provide the physical base for virtually all human activities, soils are probably the least understood of our planet's ecosystems. The ultimate goal of soil scientists is to understand all aspects of soil resources. They do so by identifying, interpreting and managing soils in connection to agriculture, forestry, rangeland, ecosystems, urban uses and reclamation. Soil science may comprise work within the realms of biology, ecology, geology, geography, chemistry, physics, microbiology, and mathematics. Careers in soil science include a wide variety of professional opportunities both within private companies, environmental and agricultural consulting firms, governmental institutions and universities. The following are examples of activities conducted by soil scientists (from the Soil Science Society of America educational website):

• conducting research in public and private research institutions
• managing soils for crop production, forest products and erosion control management
• teaching in colleges and universities
• predicting the effect of land management options on natural resources
• advising land managers of capabilities and limitations of soils
• recommending soil management programs
• helping to design hydrologic plans in suburban areas
• evaluating nutrient and water availability to crops
• managing soils for landscape design, mine reclamation, habitat conservation and site restoration
• assessing environmental hazards
• regulating the use of land and soil resources by private and public interests

Did you know? Soil scientists are also known as pedologists. In Greek: πέδον, pedon, means "soil". The term ‘pedology’ was coined by Friedrich Albert Fallou (1794-1877) who established the study of soils as an independent science, separate from geology. Vasily V. Dokuchaev (1846-1903) is commonly regarded as the father of soil science and he created the first soil classification. A crater on Mars is named in his honor.