**1. Introduction**

Climate change is the long-term shift in temperatures and weather patterns. These changes may be natural, such as through variations in the solar cycle or man-made activities. Different studies reveal that it mainly occurs due to anthropogenic activities taking place in a huge amount these days. Also, many other factors such as greenhouse effect, deforestation, urbanization, global warming, fossil fuels combustion, increased livestock farming, excessive use of fertilizers, and nitrous oxide emissions are included, which has resulted in increasing incidence of different abiotic and biotic stresses [1]. Currently, climate change is known to be the most serious contemporary challenge for humanity. The global climate conditions have been adversely affected due to different natural and unnatural activities, which have stimulated the rise in average temperature and carbon dioxide level. During the last century, the average global temperature soared up by 1.5 F, and it has been estimated that within a period

of 100 years that it might surge higher by additional 0.5–8.6 F [2]. These changes in climatic conditions have led to erratic events such as increase in rainfall and snowfall worldwide, excessive release of greenhouse gases, increase in air temperature, which renders soil dry and decreases its moisture content forming drought-like conditions, water scarcity, severe fires, rising sea levels, flooding, melting polar ice, catastrophic storms, declining biodiversity and an increase in pollution due to excessive CO2 emissions, air pollutants, ground-level ozone, aerosols, methane, and others. By altering wind patterns, it also induces seasonal variations. In other words, it involves the altering of climatic or weather patterns that occur by emission of greenhouse gases, which are likely to be more erratic and extreme in the forthcoming years [3]. Moreover, these climate-changing parameters are known to affect different terrestrial macroorganisms such as plants. However, according to recent studies, other organisms and ecosystems may be impacted as well [4]; that is, it affects human health, their ability to grow food, housing, safety, and work; for example, some people living in small islands in developing states are already more vulnerable to climate impacts.

As a result of ever-growing population, there is an increased demand of food, which has resulted in intensive agricultural practices including excessive use of agro-chemicals, livestock generation (for meat and other source of income), and exploitation of water resources, which have further worsen the situation by release of GHG (due to agricultural activities) and resulting in pollution of natural resources. The uncontrolled deforestation mainly for development and agriculture has created imbalance in the natural process of carbon cycle, which has led to a rise in the concentration of carbon footprint and brought uneven pattern of climate causing a variety of adverse effects that have huge effect on agricultural production. Due to climate change, a very high rate of land degradation has been observed causing enhanced desertification and nutrient-deficient soil, which is characterized as a major global threat. According to Global Assessment of Land Degradation and Improvement (GLADA), a quarter of land area around the globe can now be marked as degraded. Lives of 1.5 billion people have been adversely affected by land degradation caused by anthropogenic activities and climate change, and also 15 billion tons of fertile soil is lost every year, which results in mass migrations. According to a report published by United Nations Environment Programme in 2017, about 500 million hectares of farmland has been abandoned due to drought and desertification resulting in major social and environmental constraints [5].

The climate alterations highly influence the growth behavior of different crop species. For example, it has a huge impact on mineral accumulation and nutrient acquisition in the plants. Changes in morphology, physiology, and plant productivity are the direct effects observed on the plants body. The organs and membranes of plants are impaired due to different stress conditions. Due to increased oxidative stress, the production of carbohydrates, proteins, and secondary metabolite in the plants is adversely influenced. Furthermore, it also highly affects soil fertility, irrigation measures, occurrence of pests and diseases, and also, stress incidence such as heat and drought are detected. Other ill effects of climate change on production strategies observed are effects on food demand, trade opportunities, and unequal distribution of products [6]. These variations thus cause a very damaging impact on plant growth, and their developmental patterns also significantly impact the diversity and activities of different plant-associated microbial communities as they possess a huge variety of microbiomes in phyllosphere and endophytes from surrounding soil and air [7]. This beneficial microbiome present in the plants

#### *Microbial Mitigation of Drought Stress in Plants: Adaptations to Climate Change DOI: http://dx.doi.org/10.5772/intechopen.109669*

plays a vital role in regulating plant immunity, production of metabolites, nutrient uptake and acquisition, disease, and insect-pest management along with several other functions. The different microbes living in soil system comprise numerous PGPR, fungi, actinomycetes, algae, yeasts, cyanobacteria, and many more [8]. They help in transforming different organic substance into simpler form that can be assimilated by plants. Different microbiomes especially filamentous fungi and some bacterial species secrete a wide range of secondary metabolites, which are essential for plant development and many phenological responses [9]. Consequently, the microorganisms that are known for their positive effects on plant development and health might also be compromised due to climate change, in terms of exhibiting their desirable properties and their colonization capacity under certain conditions. Therefore, microorganisms present in the soil hold great importance in this regard, as they are vital constituent of nitrogen and carbon cycles and are also involved in the emission and removal of greenhouse gases such as CO2 and CH4, which in turn are mostly responsible for the climate change.
