**4.4 Impact of climate change on plant-pollinators interactions**

Climate change is directly linked to the loss of habitat, nutritional deficiencies and lack of various diets, as the abnormal climate affects the growth of plants and flowers. Flowers are forced by climate change to bloom half a day earlier each year, meaning plants are now flowering a month earlier than 45 years ago. Finally, plants that flower earlier mean that they are not pollinated and the bees and butterflies do not have any food left. A study conducted in Spain between 1952 and 2014 found that from the mid-1970s, (*Apis mellifera*) populations appeared early in the spring, as they have adapted quickly to warmer temperatures [55]. Climate change however, has the ability to disrupt the mutualism between plants and pollinators

#### **Figure 2.**

*Potential impacts of global warming on plant-pollinator interactions [56].*

and thus lead to potential mismatches, placing plant and pollinator species at risk of extinction (**Figure 2**).

The reduced co-occurrence of interacting partners, the mismatches in plantpollinator interactions may occur in a shared habitat; this decrease can be temporal or spatial. Increasing attention has been given to such types of temporal mismatches between plants and pollinating insects. A modification of the flowering period of the plant and/or the phenology of the pollinator either of which can be advanced or delayed can drive these mismatches. The co-occurrence of plants and pollinators, needed for interaction to occur, may also be spatially disrupted. The geographical overlap between interacting partners may decrease or increase during global warming, depending on the plasticity, adaptability and life history features of the species in question. In addition to temporal or spatial mismatches, climate change also has the ability to affect the interactions between plant-pollinators that are mediated by physiological or morphological characteristics. The mechanical fit of the interaction can be affected in order to have access to plant resources, in addition to plant morphology, because success of pollination depends on morphological characteristics like length of tongue or overall size of the body. For example, in many species, average rise in temperature has been shown to adversely affect the size of body. In addition, temperature rises will affect the pollinator's foraging behaviour, plant's attractiveness, together with the quality and quantity of plant resources.

#### **4.5 Impact of climate change on plants**

Whether it is heat waves, increased flooding or droughts, climate change has many impacts on plants. In addition to these global warming knock-on effects, rising concentrations of carbon dioxide and temperatures has a direct effect on the growth of plant, reproduction and resilience. Rise in local and global temperatures pose a major challenge to the growth and development of plants [57]. The Intergovernmental Panel on Climate Change (IPCC) has suggested that global temperatures would persist to rise by another 1.5°C by 2030 and 2052, if the present

## *Climate Change and Its Potential Impacts on Insect-Plant Interactions DOI: http://dx.doi.org/10.5772/intechopen.98203*

global warming patterns remain the same. Heat stress can damage all plant growth phases from the time of germination to reproduction, resulting in restricted production of important staple food crops [58]. The effect of heat stress on wheat yields, for instance is negative. For every 1°C increase in global mean temperature, a 4–6 per cent decrease in average global wheat yields is expected [59]. Climate change enforces plants to change their dates for leaves and blooming. It is suspected that warmer temperatures potentially destroy tropical forests resulting in more gases causing atmospheric warming and with increase in temperature; cold regions have become increasingly adaptable to growth of plants.

Necessary processes like photosynthesis, respiration, metabolism, and behaviour of stomata are regulated by CO2. CO2 concentrations have been rising, from around 350 ppm in 1986 to over 415 ppm in 2019 [60] and are expected to rise to 550 ppm by 2050 as reported by the IPCC. Elevated CO2 improves the efficacy of photosynthetics, and thereby improves crop growth and yield. Rubisco's improved carboxylation ability that is comparatively poor at present-day CO2 concentrations in the atmosphere has become the main reason for this improved photosynthesis. However, with increase in CO2 concentration, at the CO2 fixation site will raise the CO2/O2 ratio, contributing to the effectiveness of Rubisco's carboxylation by reducing the photorespiration rate (**Figure 3**). Under conditions of elevated CO2, an increase in root to shoot ratio was observed, in this condition plants synthesise a great number of chloroplasts, mesophyll cells, longer stems and extended diameter, length and number of large roots, more lateral root development with changes in branching patterns [62].
