Читать книгу Extreme Events and Climate Change - Группа авторов - Страница 30

In the complex production and employment context of California agriculture, climate changes such as an increase in the frequency and intensity of heat waves may have significant consequences. The impact of heat waves on human health has been widely researched in both the rural and urban contexts (Guirguis et al., 2014; Luber & McGeehin, 2008; Sahu et al., 2013; Varghese et al., 2018). Research results show that heat exposure can have significant health effects, which include heat cramps, heat stroke, heat syncope, and death. The health effects of extreme heat are both short and long term (Basu, 2015). For example, in the urban context, an analysis of survivors of heat stroke for the 2003 heat waves in France showed that victims suffered a dramatic reduction in functionality and increases in early mortality rates (Luber & McGeehin, 2008). Furthermore, the socioeconomic cost of heat waves can be significant, because research shows that the number of hospital visits during heat waves exceeds the average number of hospital visits during non‐heat wave occurrences (Guirguis et al., 2014; Luber & McGeehin, 2008; Semenza et al., 1996). The increase in hospital visits associated with heat waves also result in higher financial costs associated with emergency room (ER) visits, as well as an increase in the social costs of heat waves via mortality impacts on the elderly, the very young, and the very ill (Bell et al., 2008; Guirguis et al., 2014). Despite the development and implementation of early warning systems, the negative impact of extreme heat in both the rural and the urban sector is likely to increase in the future. Early warning systems are still not being implemented widely, and their design may result in inefficient implementation when the agents affected by heat waves are heterogeneous with respect to income or other demographic characteristics (Ebi & Schaefer, 2005). The impact of heat waves can also be highly contextual in terms of the socioeconomic profile of those affected (Bell et al., 2008; Semenza et al., 1996; Wehner et al., 2016).

In the United States, the impact of heat waves on agricultural workers’ health has been extensively researched, particularly with respect to workers who perform tasks outdoors such as harvesting (Fleischer et al., 2013; Mirabelli et al., 2010; Stoecklin‐Marois et al., 2013). Similar work has analyzed sugar cane harvesters in Costa Rica and other Central American countries (Crowe et al., 2013; Wesseling et al., 2014). Heat‐related illness (HRIs) for agricultural workers include dizziness, fatigue, fainting, nausea or vomiting, and headaches, among others. The incidence of HRIs is geographically contextual: in California, where humidity is often not a factor, the prevalence of some HRIs are different from that of Georgia or North Carolina, where humidity levels are generally higher. Studies show that the incidence of HRIs and the resulting overall impact on worker’s health is also a function of the resources and regulations that limit or enhance workers’ ability to adjust their workload to the occurrence of heat waves (Fleischer et al., 2013; Mirabelli et al., 2010; Stoecklin‐Marois et al., 2013). When appropriate regulations and compliance with those regulations take place, the impact of heat on worker’s health decrease in severity. Regular breaks, access to water, access to personal feeding times, and the use of proper clothing and protection equipment all reduce the impact of heat waves on worker’s health (Crowe et al., 2013; Kjelltrom et al., 2015).

Excessive heat (above 95⁰F to 100⁰F) can also affect worker productivity levels, possibly due to heat’s impact on workers’ health. Impact on occupational performance can be in the form of more mistakes while working and/or increases in the incidence of work‐related injuries. Research on the impact of heat on worker’s productivity has concentrated on paid agricultural work, but there is no reason to believe that heat does not affect those engaged in subsistence farming activities (Kjellstrom et al., 2016). Research has also shown that workers do not have to show HRI for productivity to decrease, because cognitive functions decline with minor elevations of body temperatures (Varghese et al., 2018). Geographically, research shows that excessive heat has significant negative impacts on the labor force located in most tropical and mid‐latitude regions of the world (Dunne et al., 2013). A research topic that has received little attention up to now is the impacts of heat on school‐age children’s ability to learn during heat wave occurrence. The long‐term impact of heat on school‐age children might very well include reductions in future labor productivity.

Although productivity impacts of heat on agricultural workers can be significant, few studies have estimated the impacts of heat on specific activities, such as harvesting. Most have estimated impacts of heat on metabolic rates in humans and assumed that after a particular metabolic threshold rate the ability of the worker to perform an activity decreases. For sugar cane harvesting workers, the metabolic threshold rate has been estimated at 261 W/m² with a corresponding wet bulb global temperature (WBGT) for harvesting at 100% effort of 79^OF. In Costa Rica the threshold values were reached, on average, at 9 am (Crowe et al., 2013). A study of the impact of heat on the productivity of rice harvesters in India found that the hourly number of rice bundles collected declined 5% per each increase in one degree in the WBGT (Sahu et al., 2013). Although these and other studies provide benchmarks of the impact of heat on productivity, they have generally assumed a linear relationship between productivity and temperature. The relationship between the onset of HRI and heat, however, is known to be nonlinear, and one could expect that the relationship between productivity and heat would be nonlinear.

Nonlinear models have been used when analyzing the impact of heat on the productivity of industrial labor (Cai et al., 2018; Somanathan et al., 2018). Research results also indicate that the impact of temperature on overall economic output in the Caribbean basin is statistically significant and of important magnitude for some sectors such as wholesale, retail, restaurants, and hotels, whereas for agriculture, hunting, and fishing the magnitude is less clear and of no statistical significance (Hsiang, 2010).

The impact of heat in agricultural labor productivity would be more complete if we were to consider a theoretical framework where other inputs required for crop production are included. In the context of the agricultural sector, this would likely require including some technological component and/or other factors of production besides labor, particularly capital and land. The next section proposes such a framework.