Strong El Niño reduces fruit production of Brazil-nut trees in the eastern Amazon

Abstract

The Brazil-nut tree (Bertholletia excelsa) is native to the Amazon rainforest, and its fruit production varies naturally with climatic conditions. Our aim was to evaluate the temporal variation in Brazil-nut production associated with climatic variables, including the strong El Niño of 2015/2016. The study was carried out in two 9-ha permanent plots in the northeastern Brazilian Amazon from 2007 to 2018: one in forest (12-year monitoring) and the other in savannah/forest transition (eight years). Overall, we monitored fruit production of 205 trees with diameter at breast height ≥ 50 cm. Annual fruit production was related to temporal series (2005-2018) of climatic data (the Oceanic Niño Index; and precipitation and air temperature from two local meteorological stations). Average fruit production per tree in 2017 was eight times lower than in 2015 and two times lower than the general average for both sites, and was significantly associated to the El Niño of 2015/2016, that increased average maximum monthly temperature and reduced the precipitation in the region, extending the dry season from three to six months. Years with higher and lower fruit production per tree coincided in both sites. Annual fruit production was significantly and negatively correlated with thermal anomalies that occurred in the third semester prior to harvest monitoring. Years with higher production were related with predominance of neutrality or the La Niña phenomenon at the global scale, and higher rainfall at the local scale. The relationship of fruit production with climate was independent of the local habitat.

Threats and Sustainability of Brazil Nut (Bertholletia excelsa Bonpl.) Pre-Industrialization in the Amazon Region

“…Regarding temperature, it was possible to observe a significant influence of temperature measurements from 1 year before seed collection. Similar results were observed by Pastana et al [18]. These authors identified a negative relationship between Brazil nut production and temperature anomalies occurring in the third quarter before harvest in the Sul do Amapá mesoregion.…”

“…However, seed production in other mesoregions may be influenced by precipitation. This was evident in the Sul do Amapá mesoregion, where an association was observed between low precipitation and reduced production [18], and in the Sul Amazonense (AM) mesoregion, where a relationship was noted between excessive precipitation and Brazil nut tree mortality [48], potentially reducing fruit production.…”

“…Research conducted by Maués in 2002 revealed that precipitation, temperature, relative humidity, and photoperiod play a role in shaping the phenology of B. excelsa [17]. Pastana et al showed that in a forest-savanna transition in the eastern Brazilian Amazon, the 2015/2016 El Niño phenomenon, when temperatures of the ocean increased more than 2°C during the dry season, fruit production decreased by up to 97% in 2017 [18]. The temporal variability in Brazil nut productivity influenced by climate oscillations pose major social and economic impacts on such forest-based extractivist communities in the Amazon, in some cases increasing by a quarter the prices of nut production unit (from USD 10 in 2016 to USD 38 in 2017) [18].…”

Size and crown shape predict reproductive maturity of Carapa guianensis in upland and floodplain forests in the northeastern Amazon

“…The climate in the region is classified as tropical savanna (Aw) and tropical monsoon (Am) by the Köppen classification (Alvares et al, 2013; Peel et al, 2007). The average annual temperature is 25°C, and average annual precipitation is 2300 mm, with rainy period from January to July and dry period from August to December (Pastana et al, 2021). The altitude varies around 150 m a.s.l.…”

Local governance, climate change, and natural resource management in the Amazon

“…This reduction in production areas could cause a 4.2% decrease in national cocoa production and affect the income of almost 9,000 families. Likewise, Pastana et al (2021), evaluating the effect of the 2015/2016 El Niño on the annual production of Brazil nuts (B. excelsa) in the Rio Cajari Extractive Reserve (Amapá), found a strong relationship between the reduction in precipitation and the increase in temperature with the decrease in Brazil nut production. The authors report that the reduction in production and the consequent low supply of Amazonian nuts in a strong market with rising prices led to invasions and conflicts in extractive units.…”