290
NA stands for not applicable since it is not technically a category within the aridity spectrum (i.e., NA ranges are all in the humid spectrum), but it is important to
note that our analysis shows locations that transitioned from NA into the arid spectrum within the analyzed time period of 1961–2017.
Results
Aridity Indices, Change/Difference, and Trends in Latin
America Between 1961 and 2017
Figure 16.4 compares the aridity indices between the periods 1960–1991 and 1991–
2017. Negative values (red colors) show a decrease in aridity index (drier conditions), while positive values (blue colors) indicate an increase in aridity index
(wetter conditions). Most of arid regions shown in Figs. 16.1 and 16.2 remain the
same (gray colors) or present lower aridity conditions (blue colors). Such is the case
in Argentina, western areas of Ecuador, Peru, and Chile. In Mexico drying up is
evident in most areas. When we observe the rest of the areas (not considered arid
regions), we can see negative values (red colors) in most of the regions, which
means a decrease in aridity index or aridification. Although these regions are not
considered arid zones, they could convert in arid areas with time.
Aridity Indices, Change/Difference, and Trends by Country
Between 1961 and 2017
The results for the aridity index averages for Latin America shown in the maps
above (Figs. 16.4 and 16.5) are summarized by country and presented in the
Appendix Table 16.3. The tables show a consistent pattern. All but three countries
(Guyana, Peru, and Uruguay) show on average a decrease in the aridity index, a
negative change difference between the two time periods analyzed (1961–1990 to
1991–2017), and a negative trend sign (the slope of a linear regression for the time
series from 1961 to 2017). This means that overall the Latin American region is getting drier. The decrease in the index is the largest in El Salvador, Nicaragua, and
Mexico. However, it must be noted that if we disaggregate trends geographically by
regions within each country, there are areas that go counter the national average (see
Figs. 16.4 and 16.5). For example, the south region of Chile presents a moderate
increase of aridity. Most of Argentina has a slight decrease of aridity. We can observe
slight to moderate increase of aridity in most regions of Brazil, Colombia, Ecuador,
and Venezuela. In Peru, there are wetter conditions along the central and south
coast, while the Central and Southern Andes show drier conditions.
E. Nickl et al.
NA stands for not applicable since it is not technically a category within the aridity spectrum (i.e., NA ranges are all in the humid spectrum), but it is important to
note that our analysis shows locations that transitioned from NA into the arid spectrum within the analyzed time period of 1961–2017.
Results
Aridity Indices, Change/Difference, and Trends in Latin
America Between 1961 and 2017
Figure 16.4 compares the aridity indices between the periods 1960–1991 and 1991–
2017. Negative values (red colors) show a decrease in aridity index (drier conditions), while positive values (blue colors) indicate an increase in aridity index
(wetter conditions). Most of arid regions shown in Figs. 16.1 and 16.2 remain the
same (gray colors) or present lower aridity conditions (blue colors). Such is the case
in Argentina, western areas of Ecuador, Peru, and Chile. In Mexico drying up is
evident in most areas. When we observe the rest of the areas (not considered arid
regions), we can see negative values (red colors) in most of the regions, which
means a decrease in aridity index or aridification. Although these regions are not
considered arid zones, they could convert in arid areas with time.
Aridity Indices, Change/Difference, and Trends by Country
Between 1961 and 2017
The results for the aridity index averages for Latin America shown in the maps
above (Figs. 16.4 and 16.5) are summarized by country and presented in the
Appendix Table 16.3. The tables show a consistent pattern. All but three countries
(Guyana, Peru, and Uruguay) show on average a decrease in the aridity index, a
negative change difference between the two time periods analyzed (1961–1990 to
1991–2017), and a negative trend sign (the slope of a linear regression for the time
series from 1961 to 2017). This means that overall the Latin American region is getting drier. The decrease in the index is the largest in El Salvador, Nicaragua, and
Mexico. However, it must be noted that if we disaggregate trends geographically by
regions within each country, there are areas that go counter the national average (see
Figs. 16.4 and 16.5). For example, the south region of Chile presents a moderate
increase of aridity. Most of Argentina has a slight decrease of aridity. We can observe
slight to moderate increase of aridity in most regions of Brazil, Colombia, Ecuador,
and Venezuela. In Peru, there are wetter conditions along the central and south
coast, while the Central and Southern Andes show drier conditions.
E. Nickl et al.