**3. Impact of climate change from ecological perspective**

For quite a few decades now, the impact of global climate change on regional climates and the associated effects on regional as well as local ecosystems have been a matter of extensive discussion. Changes in climatic conditions in different regions across the globe have adversely affected agricultural productivity, food security, various ecosystem services, and overall composition as well as quality of flora and fauna [9–11]. Some of the major outcomes of climate changes have been temperature extremes and uncertainty or unevenness in rainfall patterns, which eventually pose a threat to agricultural crops [12–14]. Variability in temperatures and precipitation has also been found to influence cropping patterns, crop yields, and phenology, i.e. leaf development, anthesis, asynchrony between anthesis and pollinators, increased respiration, decrease in pollen germination, shorter grain filling period, and lesser biomass production [12, 15, 16].

Greenhouse gas emission and/or concentration pose a threat to the flexibility and adaptability of natural ecosystems, through influencing climate change as well as ocean acidification [17]. The recent 2018 International Panel on Climate Change (IPCC) Special Report on 1.5°C alerts that drastic climate change impacts will ensue if the planet is allowed to warm beyond 1.5°C, and such impacts include drought, flood, heat waves and sea-level rise [17, 18]. Such effects would not only harm man-kind and the lifestyle we are presently accustomed to but also the natural biodiversity in general. The previously agreed upon temperature target was 2°C; however, the halfdegree variation was considered vital to avert the risk of Arctic and Coral Reef Ecosystems' degradation [17, 18]. A vital lesson to learn from this Special Report is that there is an estimated 12 years of time to reduce the net carbon emissions by half in order to avert the severe impacts mentioned earlier; however, achievement of this target would still potentially result in continued global warming as well as the associated impacts [17].

Among the most notable effects of global climate change on ecology and biosphere, salinity is number one. Several researchers have noted that one of the main reasons behind the rising levels of soil salinity across the globe is global climate change and its associated impacts, such as increasing temperature, lower precipitation, higher evapotranspiration, consequent aridisation of susceptible regions and rise in sea levels [19, 20]. Although salinity or sodicity in soil mostly originates due to natural factors such as weathering and there is some amount of it always existing in soils, the influence of climate change conditions is also substantial, whereby the amount of salinity exceeds beyond the threshold.

An important stress factor for living organisms, in particular plant life forms, is water-deficit or drought. Drought or drought-like situation arises for plants when there is inadequate water supply near the roots. This is caused by several factors such as natural climatic or geographical conditions, irregular rainfall pattern, high environmental temperature, high light intensity, spells of dry wind, water-retaining capacity of soil and water-deficit due to high transpiration rate [21, 22]. Although agricultural drought is not a big threat in itself, since it is a common natural phenomenon, and is often preceded by meteorological drought, it can still be seen as a rising abiotic stressor for plants due to the wasteful and careless anthropogenic practices. The alarming rise in greenhouse gas concentration in environment and the subsequent global warming (due to the tendency of these gases to be well mixed in atmosphere) has led to an upsurge in soil and surface water temperatures, leading to drought-like conditions. Over the past two centuries, the concentrations of carbon dioxide and methane have increased to 30% and 150%, respectively, and have thus influenced climate change through global warming and alterations in rainfall pattern [22, 23].

A direct impact of global change in climatic conditions of temperature and accumulation of greenhouse gases is thinning of the protective ozone layer of Earth's stratosphere, a phenomenon that is being studied for almost three decades now [24]. An immediate concern arising from this observation was the impact of solar UV radiation on animal as well as plant life forms. Both UV-A and UV-B are potentially harmful to biological molecules and cellular systems, and it has been noted that the interaction of UV-B with several other climate change factors (such as temperature, drought/precipitation and greenhouse gas like CO2) can further complicate its effect, as depicted in **Figure 1** [24].

It is thus understandable that climate change is leading to enhanced abiotic stress for organisms, in particular, the sessile plant beings. The ongoing section shall throw *Understanding the Impact of Global Climate Change on Abiotic Stress in Plants… DOI: http://dx.doi.org/10.5772/intechopen.109618*

#### **Figure 1.**

*Schematic overview of how UV-B affects life forms at different levels, alone as well as through its interaction with various climate change factors (derived from Caldwell* et al. *[24]).*

light on how the abiotic stress factors catalyse their detrimental effects on plants and the strategies employed by plants to tackle these effects.

### **4. The challenge of abiotic stress for plants: Harms and defence strategies**

As discussed in the preceding section, salinity is one of the significant stressors for plants and is currently being elevated by climate change conditions. It is crucial to discuss the impact of salinity stress because according some reports, and it is estimated that salt-affected land is leading to a loss of approximately 12 billion USD annually, and future predictions for agricultural production highlights the significance of working efficiently under high saline conditions [25]. Some of the principal ways by which salinity manifests its adverse effects on the physiology and biochemistry of plant systems are as follows:


photosynthetic pigment concentrations and photosynthetic efficacy together under increasing saline stress are attributed to loss of photosynthetic-membrane integrity, destruction of proteins and enzymes in photosynthetic pathway, dehydration of cell membrane leading to reduction in CO2 permeability, enhanced senescence, alteration in enzymatic activities due to morphed cytosolic integrity and negative feedback by reduced sink activity [26].

Apart from salinity, abiotic stressors such as drought and UV-B radiation are also currently on the rise due to climate change conditions. Some of the principal effects of drought and excess UV-B light on plant systems are as follows:


In addition to the points mentioned above, all the abiotic stress factors discussed herein are also potential contributors to the rise in cellular concentrations of ROS. As rightly pointed out, all kinds of stress eventually lead to a rise in ROS

*Understanding the Impact of Global Climate Change on Abiotic Stress in Plants… DOI: http://dx.doi.org/10.5772/intechopen.109618*

#### **Figure 2.**

*Schematic overview of oxidative stress effects induced due to ROS overproduction (Taken from Dutta* et al. *[39]).*

concentrations beyond their threshold value, thereby manifesting symptoms of oxidative stress [38]. The same has been depicted in **Figure 2**. Moreover, climate change conditions have also witnessed a rise in biotic stress for plants, in particular for the agronomically important plants, for instance, heightened pathogenic and pest stress, and weed stress [39].

Even though there is an upsurge of stressing conditions for plants, these immobile yet versatile organisms prove their resilience by strategically responding to the environmental stressors. Some of the major defence strategies employed by plants against the abiotic stress factors have been depicted in **Figure 3**.
