Amazon Droughts

Severe droughts reduce river navigability and isolate communities in the Brazilian Amazon

Point of Departure

It is hard to imagine that the Amazon can reach such an extreme state of dryness that can even disrupt navigation through some of its largest rivers...


But that is what has been happening much more frequently than expected.

The 2023 Drought

The most recent drought, in 2023, afflicted more than half a million people in the Brazilian Amazon basin, making it one of the most severe droughts ever recorded. The drought was accompanied by enormous fish kills and the deaths of hundreds of river dolphins, all caused by extremely high air and water temperatures and low water levels in large areas. Tens of thousands of remote rural settlers along rivers were completely cut off from urban hubs and adjacent towns for weeks or months.


Photo credits: João Paulo Borges @drone_da_amazonia




Past Severe Droughts

The severe drought of 2023 was not an isolated event. Studies have shown that the Amazon is undergoing an intensification of extreme events, both droughts and floods.

In our study, we found that the severe droughts of 2005, 2010, and 2015-2016, were not only abnormally intense, but also lasted longer than usual. We counted the number of days per hydrological year in which water levels during dry periods were lower than a historic threshold using data from 90 river gauging stations.

Past Droughts

During the droughts of 2005, 2010, and 2015-2016, low water levels lasted more than one additional month compared to average conditions.



This graph presents the number of days per hydrological year in which water levels were lower than expected during the dry season, considering the records of 90 river gauging stations. For the threshold we chose, low water levels are expected 20% of the time in a year (that is, around 73 days, as stressed by the bold line), but during severe droughts, for most river stations under analysis, low water levels endured more than 100 days instead. Number of days is shown in parenthesis on top. P.S.: not all gauging stations had data for all years. Check the paper for methodological details. Here the hydrological year is set to start in Dec 1 of previous year. Source: Santos de Lima et al. (2024) Comms. Earth & Env. doi: 10.1038/s43247-024-01530-4.

Impacts on Navigation

During severe droughts, low water levels constrain river navigation due to the lack of adequate water depth. As large sandbanks and boulders become exposed, river channels narrow down, restricting accessibility. As a result, boats and ships may dock far from ports, making it difficult for passengers to get to shore or requiring them to walk across the massive sandbanks. To prevent accidents, navigation speed is substantially decreased, and zig-zag routes are done to avoid obstacles. The Brazilian Navy issues warnings and may also impose restrictions on nighttime navigation, maximum speed, and vessel draft.

Navigation through rivers and wetlands is the most important form of transportation for most of the Amazonian population. It is particularly important, however, for rural communities, which rely on boats as a means to undertake regular daily activities such as reaching urban centres, schools, and healthcare facilities, trading their forest and agricultural products, reaching fishing and hunting sites, and visiting family members and friends in other towns.


A typical regional boat carrying load and passengers docked at Manaus Port, Amazonas, Brazil. Photo credits: Letícia Lima

Travelling by boat is an essential part of the Amazonian culture and way of life, even for urban residents. Besides, navigation is fundamental for the supply of food, medicine, fuel, and other goods to rural villages. It is also the means through doctors, nurses, and government officials can reach these communities. When a severe drought strikes, access to services and goods become highly affected.


A traditional form of travelling by boat for Amazonians. Long trips are endured by resting in hammocks with their belongings nearby. Photo credits: Letícia Lima





Distance to major water bodies and roads

Isolation during Droughts

We analysed the shortest distance between human settlements and major water bodies (rivers and wetlands) as well as roads in order to identify those locations that would, in theory, rely more on navigation than on terrestrial transportation. This indicator, although simple, allowed us to spot the non-Indigenous localities and Indigenous villages that are prone to some degree of isolation during severe droughts. This result might help decision-makers prioritise specific regions of the Amazon.

Isolation during Droughts

Nearly half of non-Indigenous localities and 54% of Indigenous villages of the Brazilian part of the Amazon are prone to isolation during severe droughts.

In our study, we found that nearly half of non-Indigenous localities as well as 54% of Indigenous villages are prone to some degree of isolation during severe droughts taking into consideration their distance to major water bodies and roads. The Amazonas State (AM) stands out with nearly 78% of its localities prone to isolation (n = 1,495) as well as 77% of its Indigenous villages (n = 755). Around 41% of the Indigenous villages in Roraima State (RR) (n = 225) could also be prone to isolation as well as 68% of those in Acre State (AC) (n = 125).


The maps above present the distribution of (a) non-Indigenous localities, and (b) Indigenous villages that are prone to isolation during severe droughts (yellow and red points, respectively). We categorized as “prone to isolation” those settlements that are more than 5 km away from the nearest road and less or equal to 5 km away from major water bodies. Source of base data: IBGE, 2021 (localities and state borders), FUNAI, 2020 (Indigenous villages), Fleischmann et al., 2022 (inundation extent, base map in blue), ANA 2017 (basin borders). Figure source: Santos de Lima et al. (2024) Comms. Earth & Env. doi: 10.1038/s43247-024-01530-4.
A traditional floating house stranded in a large sandbank near Tefé, Amazonas, Brazil. Photo credits: João Paulo Borges @drone_da_amazonia

Spatio-temporal assessment of impacts

Digital Media Analysis

To evaluate the exposure of Amazonian communities to past extreme drought events, we collected and analysed digital news articles reporting impacts of droughts from 2000-2020. We identified a total of 70 news articles, from which we extracted 142 statements. After accounting for each location mentioned in the statements (one statement could mention multiple locations), we documented 224 entries. We extracted metadata regarding year, month, and location of the reported impact and then identified administrative boundaries and the closest river gauging stations.

The years 2005, 2010, and 2016 were noteworthy in terms of the number of media articles reporting impacts of droughts. Localized impacts were also reported in other years. The impacts of the droughts in 2005 and 2010 were mostly reported in the months of September, October, and November, while the 2015-2016 drought was more widespread, with news articles pointing to impacts across several months.


Distribution of news media articles per year and per months. Figure source: Santos de Lima et al. (2024) Comms. Earth & Env. doi: 10.1038/s43247-024-01530-4.

Analysing the spatial distribution of these news articles, 2005 and 2010 registered substantial impacts on local populations, particularly in the central and western Brazilian Amazon. In 2005, news documented impacts on rural areas of the Purus, and lower Negro River basins as well as southern tributaries of the Solimões River. Accounts indicate that the drought of 2010 might have affected over half of the Brazilian portion of the Amazon basin, covering the Madeira, Purus, Juruá, and Negro River basins, as well as the Solimões tributaries. 2015-2016 was a particularly strong drought with collected news accounts showing effects across the Amazon basin, including the Madeira, Xingu, Juruá, and Purus River basins. Notably, the Negro River basin made headlines in nearly half of the years from 2000-2020.


Spatio-temporal distribution of news media articles reporting impacts in the Brazilian part of the Amazon basin. Figure source: Santos de Lima et al. (2024) Comms. Earth & Env. doi: 10.1038/s43247-024-01530-4.

Passenger and load transportation are frequently reported in the news as directly affected by droughts. Reports indicated that droughts compromised access to essential goods such as food, fuel, and medical supplies, largely due to impacts on load transportation, particularly affecting riverine communities. Impacts were felt in the form of scarcity of goods, delays in product delivery, higher prices due to logistical constraints, and even the complete lack of products such as medicine in some regions. Logistical issues due to low water levels increased transportation costs and time, leading to an increase in food prices that affected local businesses and threatened food security. Transportation disruptions also restricted the ability of rural dwellers to sell their own products to regional markets.


Number of statements extracted from news articles categorized by type of activity impacted by droughts. Figure source: Santos de Lima et al. (2024) Comms. Earth & Env. doi: 10.1038/s43247-024-01530-4.

Unfolding Impacts

Droughts cause cross-sectoral cascading impacts on the population of the Amazon, often triggered by their effects on river levels and resulting constraints on navigation.



Cross-sectoral cascading impacts on the population of the Amazon, particularly threatening to remote rural communities, such as Riverine ("Ribeirinhos") and Indigenous groups. Figure source: Santos de Lima et al. (2024) Comms. Earth & Env. doi: 10.1038/s43247-024-01530-4.

Key Take-Aways

Developing Long-Term Strategies

Conventional emphasis on single or direct impacts is not enough to design effective policies to cope with and adapt to droughts in the Amazon. Effective policies should be grounded in preparedness and adaptation principles, and based on long-term planning.

Lessons from previous droughts

(1) Severe droughts were not only intense, but also lasted more than a month longer than in average years.


(2) Impacts on the population are of several sorts, but many of them are mediated by the effects of low water levels on navigation.


(3) Impacts are intersectoral and cascading, leading to stronger consequences for remote rural communities.


(4) In the Brazilian context, human settlements that are prone to isolation during droughts are clustered in the Amazonas State, although other states can also face impacts.

Recommendations

(1) Spatial assessments can be used to identify in advance settlements prone to isolation and prioritize areas in preparation for upcoming droughts.
(2) It is paramount to count on early warning systems to prepare and equip vulnerable communities in advance of prolonged droughts.
(3) Roads are not the solution: there is robust scientific evidence linking roads to deforestation and longer dry periods, aggravating droughts. It also accelerates soil erosion and siltation in river channels, impairing navigation even more.
(4) Cross-national strategies spanning all Amazonian countries are required for effective long-term adaptation planning.


Science Outreach

Working with school kids

Severe droughts are expected to happen more frequently. Awareness should be raised among citizens and organizations. This conversation should also involve the young generation. Click on the image below to download our coloring material to talk about droughts with kids.

Reach Out

Acknowledgements



The authors acknowledge the fruitful exchange of ideas with Andrea Castanho (Woodwell), Michael Coe (Woodwell), Foster Brown (UFAC), Esteve Corbera (ICTA-UAB), and colleagues from the “SPSAS Sustainable and Inclusive Amazonia” (Programa Biota FAPESP). Letícia Lima thanks to AGU Voices for Science Program for its science outreach mentorship.



Webdesign: Markus Kreutzer

Web Content: Letícia Lima

Webdesign assistance: Balam Castro

Graphic design support: Markus Kreutzer

Photos: João Paulo Borges & Letícia Lima

Funding

Beatriu de Pinós Fellowship (Generalitat de Catalunya, 2020-BP-00156); LASEG - Universitat Autònoma de Barcelona and Generalitat de Catalunya (2021-SGR-00182); “María de Maeztu” Units of Excellence, Gov. of Spain (CEX2019-000940-M); Moore Foundation (#9957); NSF (DEB#1950832); NASA(IDS#80NSSC24K0301).


Contact


Letícia Santos de Lima - leticia.lima@uab.cat

Marcia Macedo - mmacedo@woodwellclimate.org

leticialima.weebly.com



Materials


Access the article here.

Access the dataset here.

Study Authors

Letícia Santos de Lima

Francisco Eustáquio Silva

Paula Dorio Anastácio

Marina Marcela Kolanski

Ana Carolina Pires Pereira

Marianne Stéfanie Menezes

Evandro Paradela Cunha

Marcia Macedo

Institutions Involved

ICTA-UAB, Spain

UFMG, Brazil

Woodwell Climate, USA

IPAM, Brazil

Espace-DEV, France