Resistance of African tropical forests to an extreme climate anomaly

Please download the Document here below:

e2003169118.full

 

Abstract

 

The responses of tropical forests to environmental change are critical uncertainties in predicting the future impacts of climate change. The positive phase of the 2015–2016 El Niño Southern Oscillation resulted in unprecedented heat and low precipitation in the tropics with substantial impacts on the global carbon cycle.

 

The role of African tropical forests is uncertain as their responses to short-term drought and temperature anomalies have yet to be determined using on-the-ground measurements. African tropical forests may be particularly sensitive because they exist in relatively dry conditions compared with Amazonian or Asian forests, or they may be more resistant because of an abundance of drought-adapted species.

 

Here, we report responses of structurally intact old-growth lowland tropical forests inventoried within the African Tropical Rainforest Observatory Network (AfriTRON). We use 100 long-term inventory plots from six countries each measured at least twice prior to and once following the 2015–2016 El Niño event.

 

These plots experienced the highest temperatures and driest conditions on record. The record temperature did not significantly reduce carbon gains from tree growth or significantly increase carbon losses from tree mortality, but the record drought did significantly decrease net carbon uptake. Overall, the long-term biomass increase of these forests was reduced due to the El Niño event, but these plots remained a live biomass carbon sink (0.51 ± 0.40 Mg C ha−1 y−1) despite extreme environmental conditions. Our analyses, while limited to African tropical forests, suggest they may be more resistant to climatic extremes than Amazonian and Asian forests.

 

Tropical forests are a critical component of the global carbon cycle because they are extensive (1), carbon dense (2), and highly productive (3). Therefore, consistent impacts on these forests can have global consequences. Their global importance is seen via atmospheric measurements of CO2, showing a near-neutral exchange of carbon across the terrestrial tropics; hence, the large carbon losses from deforestation and degradation are offset by the significant carbon uptake from intact tropical forests and tropical forest regrowth (4). Independently, ground observations of structurally intact old-growth tropical forests also show this uptake, with forest biomass carbon increasing across remaining African (5, 6), Amazonian (7), and Asian (8) forests. Yet, unlike in Amazonia (9, 10) and Asia (8), the impact of a severe drought or a drought and high-temperature event in African tropical forests has never been documented using ground data.

 

High temperatures test the physiological tolerance of tropical trees. Above optimal temperatures, plants reduce their carbon uptake (11). This includes closing stomata to avoid water loss, reducing internal CO2 concentrations, and reducing carbon assimilation in the leaf. Higher temperatures increase vapor pressure deficits (12) and alongside reduced precipitation, increase the chance of hydraulic failure (13). Individually or in combination, these impacts can slow growth and may eventually kill trees (14), although tropical seedling growth can increase with experimental warming (15). As well as reduced carbon uptake, plants use more carbon under higher temperatures; respiration rates tend to increase with short-term increases in temperature both at the leaf (16) and forest stand (17) scales, again reducing tree growth and potentially leading to tree death via carbon starvation (18). Recent analyses of tropical forest plot data showed increased temperatures over the prior 5 y were associated with lower levels of carbon uptake from tree growth and higher levels of carbon loss from tree mortality (6). Furthermore, biome-wide spatial analyses suggest the existence of a temperature threshold above which carbon uptake from tree growth declines rapidly (19). Thus, with high temperature anomalies, we expect reduced tree growth and increased tree mortality.

 

Drought also impacts trees as water deficits can slow tree growth and if of sufficient strength or duration, can kill trees, either via hydraulic failure or carbon starvation. Hydraulic failure of the xylem has been found across species and biomes in response to drought, while carbon starvation has been documented in some locations including one tropical site (20). Inventory plot observations before, during, and after droughts show the impacts of drought in Asia and Amazonia. In Asia, the 1997 to 1998 El Niño temporarily halted the carbon sink in live biomass in Bornean forests by increasing tree mortality (8, 21). In Amazonia, severe droughts in 2005 and 2010 elevated biomass mortality and in 2010, also significantly reduced tree growth (9, 10). The Amazon biomass carbon sink was reversed by the 2005 drought, and while it rapidly recovered, it is weaker since 2005 (7), potentially due to high-temperature impacts (6). However, while the impacts of short-term drought in their long-term context have been investigated in Amazonia and Asia, in Africa we so far lack any ground-based assessment of large-scale drought impacts due to a paucity of observations.

 

Although the broad responses of African tropical forests to temperature and drought anomalies might be hypothesized from first principles and the responses of other continents, there are considerable uncertainties. On the one hand, there are grounds for expecting African forests to be especially vulnerable. African forests are already remarkably dry compared with Amazonian and Asian tropical forests, with almost 90% receiving <2,000 mm y−1 precipitation (22), the approximate amount necessary to maintain photosynthesis at high levels throughout the year (23). This low rainfall suggests African tropical forests may already be close to their physiological and ecological limits. Additionally, the lower temperatures African forests tend to experience—as many are situated at slightly higher altitude than forests in Amazonia—could result in limited species tolerace of high temperatures. African forests are also much less species rich than forests in Amazonia and Asia (2, 24), with a relative lack of species in high-temperature African forests (25), and this lower diversity could conceivably drive lower resistance to climate anomalies (26).

 

Alternatively, the relatively dry conditions of African tropical forests may, perhaps counterintuitively, confer drought resistance. African climate has oscillated between wetter conditions in interglacial periods and cooler and drier conditions in glacial periods (27), so the African pool of species present today may be more drought tolerant because some of the most mesic-adapted biodiversity has been lost over time (28, 29). Drier African tropical forest tree diversity is similar to that of the Amazon or Asia, but tree diversity does not increase with shorter dry seasons in Africa as it does in Amazonia (25), suggesting that most wet-adapted species have been lost and either the dry-adapted species remained or these lineages have diversified more, potentially conferring drought resistance. Indeed, a 40-y drought in West Africa led to an increased abundance of deciduous species in tropical forests in Ghana (30, 31). The relatively cool conditions of African tropical forests might also imply resistance as these forests are further from a potential high-temperature threshold that may limit photosynthesis. Overall, African tropical forests could plausibly be more or less vulnerable to temperature and drought anomalies than Amazonian tropical forests.

 

Understanding how intact African forests respond to climate anomalies is vital, not least because they have been providing a substantial long-term carbon sink, reducing the rate and magnitude of climate change (5, 6). The impacts of environmental change on African tropical forests are also important because of unique aspects of their structure. African forests typically have high aboveground biomass and so, high carbon storage per unit area—on average, one-third more than Amazon forests (2, 32, 33). African forests are composed of a smaller number of stems, ∼425 ha−1 (≥100-mm diameter), compared with ∼600 ha−1 in Amazonia and Asia (32) and so, are more dominated by large trees. Hence, even small decreases in growth of the large dominant trees or modest increases in the mortality of these trees could lead to large carbon stock reductions and a loss of the live biomass carbon sink.

 

The 2015–2016 El Niño event provided a first opportunity to assess the impact of high temperatures and strong water deficits on the ∼450 Mha (6) of African tropical forests. While three very strong El Niño events have occurred in the last 50 y (1982 to 1983, 1997 to 1998, and 2015 to 2016), only the latter occurred after a network of long-term inventory plots had been established in Africa and was poised to capture an El Niño event (5). At the onset of the 2015–2016 El Niño, we organized a specific “emergency” six-nation remeasurement program to capture the impact of the climate anomaly on African tropical forests. We therefore combine climate data with measurements from 100 African Tropical Rainforest Observatory Network (AfriTRON) long-term inventory plots that were remeasured to capture the 2015–2016 El Niño event to address the following questions. 1) Did African tropical forests experience unprecedented temperature anomalies in the 2015–2016 El Niño? 2) Did African tropical forests experience unprecedented drought in the 2015–2016 El Niño? 3) Which climate anomalies drove forest responses to the 2015–2016 El Niño? 4) What were the overall impacts on the monitored old-growth structurally intact tropical forests?

 

Please download the Document here below:

e2003169118.full

Go back

Partners News

RDP 19: Registration Schedule

Registration for the 19th Meeting of the Parties of the PFBC from July 5 - 8, 2022 started yesterday July 03 from 10:00 to 13:00 and from 14:00 to 18:00. If you have not yet registered, please go to the Radisson Blu Hotel, on the 1st floor in front of the Libreville 1 room according to the days and times below...

Field Trip Registrations prolonged until Sunday!

Registration for field trips for the CBFP MoP19 has been prolonged until Sunday, 26 June 2022 at 6pm CEST. These exclusive field Trips will kick-off the diverse and ambitious technical and political discussions that will take place during the MoP19. They will offer great scenery and expert inputs on a variety of relevant themes. Field trips will take place before the beginning of the official meetings, between July 02 and 04, 2022.

2021 FERN Annual Report

Firstly, the European Commission (EC) published its breakthrough proposal for a EU Regulation on deforestation-free products, which Fern and allies have been working towards for years. We also came together with partner NGOs and civil society groups from around the world to successfully campaign to stop the EU from discarding Forest Law Enforcement Governance and Trade Voluntary Partnership Agreements - its best weapon to fight against illegal logging.

MOP19 Libreville Field Trip: Registration Now Open!

To kick off the diverse and ambitious technical and policy discussions that will take place during the conference, we are pleased to offer several field trip opportunities exclusively for MOP19. These will include beautiful landscapes and tours led by experienced experts on a variety of topics. The field trips will take place prior to the start of the conference, between July 02-4, 2022.

Registration opens for exhibitors at the CBFP MOP 19 Exhibition Centre

We are pleased to hereby inform you that exhibition registration for the CBFP MoP19 is open. The exhibition space offers your organization the opportunity to present your work, initiatives, projects and expertise to the participants of the MoP19. Exhibitors are able to rent a stand package at set prices with options for customization and additional equipment. To register as Exhibitor at the 19th Meeting of Parties of the Congo Basin Forest Partnership (CBFP), please fill out this form online before June 10, 2022.

In the DRC’s forests, a tug-of-war between oil and aid – MONGABAY

At the COP26 climate summit, U.K. Prime Minister Boris Johnson and President Féelix Tshisekedi of the Democratic Republic of Congo announced a $500 million aid package to protect forests in the Central African country. Part of the Glasgow Leaders’ Declaration on Forests and Land Use, the announcement was one of the top headlines at the summit.

Convention on the Conservation of Migratory Species of Wild Animals – CMS

Bonn/Ventotene 26 May 2022 – Visualizing how migratory animals connect continents, countries, sites and habitats is the result of an international scientific effort under the aegis of the Convention on the Conservation of Migratory Species of Wild Animals (CMS), in developing the first atlas of bird migration across three continents. CMS, an environmental UN treaty, will launch the Eurasian-African Bird Migration Atlas today at the Museum of Migration on the Italian island of Ventotene, as the first part of a broader initiative to develop a global atlas of animal migration.

Save the Children signs deal to lead on climate change adaptation in the Pacific where children bear the brunt of extreme weather

Save the Childrenwill deliver the Pacific region’s largest ever investment in community-based climate change adaptation in one of the world’s biggest climate hotspots, the child rights organisation announced today.

Green Climate Fund Board approves USD 325.2 million and policies for accelerated climate action

The Green Climate Fund (GCF) Board has closed its 32nd meeting, approving four new climate projects worth USD 301.5 million in GCF funding and USD 1.7 billion in co-financing. Including the approval of tranche two funding for an approved project, USD 325.2 million of GCF funding was approved for climate action.

Experts map matrix of certification standards at World Forestry Congress - forestsnews

Establishing certification standards for forestry and agricultural commodities is no straightforward matter, particularly for smallholder farmers. Voluntary standards of the type designed by the Forest Stewardship Council (FSC) ensure timber and non-timber forest products are produced according to sustainability standards and audited by a third party. They have been used to tackle deforestation, forest degradation and ensure ethical trading practices for more than 30 years.

“Existential threats,” harsh warnings and hope in U.N. Global Land Outlook – ATIBT

“At no other point in modern history has humanity faced such an array of familiar and unfamiliar risks and hazards interacting in a hyper-connected and rapidly changing world,” said Ibrahim Thiaw, the executive secretary of the U.N. Convention to Combat Desertification (UNCCD), in a statement on the launch of the second Global Land Outlook report (GLO2).

Relaunch of the National Forest Stewardship Standard development process in the Democratic Republic of Congo – ATIBT

FSC's Principles and Criteria set out the global requirements for responsible forest management. Chamber-balanced standard development groups (SDG’s) adapt the International Generic Indicators at the regional or national level to reflect the diverse legal, social and geographical conditions of forests in different parts of the world. The resulting adjustment is incorporated into a National Forest Stewardship Standard.

19th Meeting of the Parties (MOP) July 5-8, 2022, in Libreville, Gabon: Registration has been extended to June 01, 2022!

If you wish to attend the 19th MoP of the CBFP and related events, please register before June 02, 2022 by completing the form below and clicking on the button “register”. It will not be possible to attend the meeting without a properly completed registration procedure.

Forum ATIBT : D-7!

With just over a week to go before the ATIBT Forum, we are sharing an updated version of the conference and roundtable program.This program will be regularly updated on the ATIBT website page dedicated to the Forum.

Environment and Peace Call for Proposals

PeaceNexus is launching a call for proposals on embedding conflict sensitivity in environmental organisations. Environmental organisations are at the forefront of addressing the triple planetary crisis of climate change, pollution and biodiversity loss. In doing so, they grapple with conflict dynamics, face risks to their staff and partners, but also provide opportunities for divided groups to work together around issues of common concern. The deadline for application is Tuesday 21st June 2022.

19th Meeting of the Parties, July 5-8, 2022, in Libreville, Gabon: Registration is closing on May 20, 2022!

This is a reminder that registrations for the 19th Meeting of Parties (MoP) of the Congo Basin Forest Partnership in Libreville, Gabon, from 5 to 8 July 2022 are CLOSING IN 2 DAYS. Please note, that you can only attend with a completed registration. Please register here...

Mongolia flood defence project shows the way for urban adaptation - The Green Climate Fund

Mongolia flood defence project shows the way for urban adaptation. The project incorporates infrastructural upgrades with the formation of community action groups to improve the capital’s flood resilience . A project in Mongolia, which incorporates a wide range of initiatives and aims to build the resilience of high-risk communities, is directly confronting the burden of urban climate impacts.

 

The Green Climate Fund (GCF) Board holds second meeting of 2022

The 32nd meeting of the GCF Board is taking place in person in Antigua and Barbuda from May 16-19. The meeting, one of four scheduled this year, follows on the heels of the first Board meeting where USD 187.7 million was approved for new climate projects and major changes to GCF’s accreditation framework were approved.  The changes aim to accelerate climate finance for developing countries and include strengthening the existing accreditation model and introducing the project-specific assessment approach (PSAA).

Expert meeting on the EU Regulation on deforestation-free products – FERN

The proposed EU Regulation on deforestation-free products aims to ensure goods cannot be placed on the EU market if they have caused deforestation, forest degradation, or violated producer country laws. The Commission released a draft proposal of the Regulation on 17 November 2021, and now the European Parliament (EP) and the Council must agree on their positions. On 24 March 2022, the EP rapporteur Luxembourgish Member of the European Parliament (MEP), Christophe Hansen of the centre-right European People’s Party (EPP), released his draft response.

New International Maritime Organization guidelines to combat wildlife smuggling – TRAFFIC

Global shipping to focus on bringing down the illegal networks exploiting maritime supply chains to traffic wildlife. On the 13 of May 2022, the 46th Meeting of the Facilitation Committee (FAL46) of the International Maritime Organization (IMO) adopted new ‘Guidelines for the Prevention and Suppression of the Smuggling of Wildlife on Ships Engaged in International Maritime Traffic’.

Brief Highlights Role for Human Rights-based Approach to Achieve SDG 6 - IISD

Fifty years after the 1972 Stockholm Conference on the Human Environment, which put “health and sanitation” on the international agenda, ensuring water and sanitation for all “remains one of the world’s biggest challenges.” A ‘Still Only One Earth’ policy brief from IISD argues that for universal access to become a reality,

UNCCD’s Global Land Outlook Calls for “Activating” Land Restoration Agenda – IISD

The UN Convention to Combat Desertification (UNCCD) has issued the second edition of its flagship report titled, ‘Global Land Outlook: Land Restoration for Recovery and Resilience’ (GLO2). The publication outlines various future land scenarios, and highlights the potential contributions of land restoration investments to climate change mitigation, biodiversity conservation, poverty reduction, and human health, among other SDGs.

World Congress Urges Shared Responsibility Over Forests for Multiple SDGs – IISD

Delegates at the 15th meeting of the World Forestry Congress (XV WFC) called for immediate action to protect forests, forestry, and forest stakeholders as providers of nature-based solutions to climate change, biodiversity loss, land degradation, hunger, and poverty. They encouraged “actions for a green, healthy and resilient future with forests” as a contribution to the SDGs, the UN Decade on Ecosystem Restoration, the post-2020 global biodiversity framework, and a green recovery from the COVID-19 pandemic.

FAO Flagship Outlines Forest Pathways for Tackling Planetary Crises - IISD

The Food and Agriculture Organization of the UN (FAO) has launched its biennial flagship report on the state of the world’s forests (SOFO), which explores three intertwined forest pathways to achieve green recovery from the COVID-19 pandemic while tackling climate change and biodiversity loss, among other “multidimensional planetary crises.”

Desertification and Drought Day Calls for New Social Contract for Nature – IISD

A high-level panel marked Desertification and Drought Day 2020 with a discussion focused on the Day’s theme, ‘Food. Feed. Fibre,” and the question, “Is it time for a new social contract for nature?” Ministers and agency heads offered recommendations for addressing vulnerabilities for land management that have been exposed by the COVID-19 pandemic and options for building back better.

The XV World Forestry Congress was held in Seoul from May 2 to 6 – ATIBT

Convening under the theme “Building a Green, Healthy and Resilient Future with Forests,” the Fifteenth meeting of the World Forestry Congress (XV WFC) sought to define the role of forests in the 2030 Agenda for Sustainable Development and other major agreements, including the Global Forest Goals, the Paris Agreement on climate change, and the post-2020 global biodiversity framework.