**1. Introduction**

In 1998, the World Meteorological Organization (WMO), a United Nations agency, and the United Nations Environment Programme (UNEP) started actions of Intergovernmental Panel on Climate Change (IPCC), which is composed of a large group of researchers from various nationalities with the aim of developing scientific knowledge about climate change and its impacts on society. It is agreed that the increase in the concentration of greenhouse gases (GHG) is mainly caused by the burning of fossil fuels and changes in land use, such as deforestation. These and other human activities are responsible for climate change [1]. The alert for these changes has promoted several lines of research within climate science to debate and create understanding about the GHG cycle and how man would be influencing this cycle, which still has great uncertainties. To decrease these uncertainties, in situ measurements are necessary to better understand the particularities of each environment [2], as these data can be used for the evaluation of soil-vegetation-atmosphere interaction models, [3, 4], as well as in the analyses of satellite products that estimate components of the water and/or CO2 balance [5–7], which can provide reliable information to monitor CO2 exchange in tropical forests that have little coverage of towers equipped with Eddy Covariance (EC) system, for example Brazil.

One practical way to mitigate the effects of climate change would be to increase the vegetation cover in dryland and devastated areas, both through the replanting of large forest covers in order to capture atmospheric CO2, and through the effect of forests on the hydrological cycle. With the emerging trade in carbon credits in the global market, there are several enterprises that benefit from the reforestation of large areas of land and the banks of hydroelectric power generation dams. Although carbon credit trading is accused of being an ineffective way to mitigate CO2 emissions, because some people pay to continue polluting, this would be an advantageous way of transitioning to an economy with a clean energy matrix, especially in a country like Brazil, with extensive areas of tropical forest.

Therefore, it would be more economically advantageous to preserve untouched forests than to devastate them for logging or to start immediately profitable agricultural and cattle ranching enterprises. However, the prognoses for Brazilian forested areas related to global warming [8, 9], especially the Amazon, are not very good: Global warming is expected to increase temperatures in this region, which may make the climate drier, causing savannization of this forest, i.e., parts of the forests should be altered, changing their structure and approaching the Cerrado physiognomy.

River levels may present a great reduction, and the air should become drier during dry periods, which increases the risk of fires. In addition, the advance of the agricultural frontier, if maintained at current levels, is expected to reduce forest cover to 53% of the original by 2050. The number of studies on the response of Amazonian and Cerrado flora and fauna species to climate change is still very small, but they indicate that with an increase of 02–03°C in average temperature, up to 25% of the trees in the Cerrado and about 40% of the trees in the Amazon could disappear by the end of this century [10]. For the planet's temperature not to exceed an increase of 1.5°C and thus avoid drastic changes in the climate, "rapid, vast and unprecedented changes" will be necessary at the global level, warned a report released on 08/10/2018 by the UN IPCC.

Micrometeorological studies to obtain data that help understand the role of Brazilian tropical forests in the planet's climate balance exist since the 1980s until the LBA (Large Scale Biosphere-Atmosphere Experiment in Amazon) [11]. Some works pointed in the Amazon forest a potential sink of atmospheric CO2 [12–14] with micrometeorological measurements. Saleska et al. [15] compared micrometeorological estimates and biometric measurements in Santarém- PA and reported a CO2 source to the atmosphere of 1.3 Mg C ha<sup>1</sup> year<sup>1</sup> , associated with the prevalence of emissions

*The Relevance of Maintaining Standing Forests for Global Climate Balance: A Case Study… DOI: http://dx.doi.org/10.5772/intechopen.110533*

by necromass decomposition in preceding episodes of high tree mortality in the region. Miller et al. [16] reported slightly positive ecosystem fluxes of 0.4 Mg C ha-1 year-1, closer to neutral, corroborated by biometric measurements. Espírito Santo et al. [17] combined satellite estimates and field data to suggest that uptake by living trees exceeds emission by dead trees, reinforcing evidence of the upland forest acting as a carbon sink in aboveground biomass. The differences between the contributions of different Brazilian biomes have been consistently reported in the literature [2]. Evapotranspiration rates are highest and greatest at Cerrado and Pantanal sites in wetter months. Even in the month with the highest evapotranspiration rates (October), the values of the Caatinga sites do not reach the magnitude scale of the measurements of the other sites, showing the peculiarity of this site as to its BSh (Arid/Stepp/Hot) climate by Köppen's climate classification. Generally the measurements show that evapotranspiration in the dry season is higher than in the wet season and Rn is the main control of evapotranspiration in humid tropical rainforests (like the Amazon site), which does not apply for the more arid Caatinga region nor for the Cerrado and Pantanal sites, which differ from the Amazon by showing depletion of evapotranspiration throughout the dry season, culminating with lower values in drier months such as August and September, the same period where the Amazon site presents its maximum [2].

All these particularities directly influence the local and regional carbon balance, showing the need to create a better understanding of the biogeochemical cycles in these locations to try to show the importance of forest climate control on climate and greenhouse gas emissions, in order to prove that keeping the forest standing can be the most viable alternative for a public policy on climate change mitigation, results that will be discussed below.
