Editing IPCC:AR6/WGII/Cross-Chapter-Paper-7 (section)

=== CCP7.3.4 Current Climate Risks for Tropical Forests ===

<div id="h2-7-siblings" class="h2-siblings"></div>

Impacts of climate change on tropical forest cover seem to correlate with climatic zone. Natural selection of drought tolerant species is observed in tropical dry forests under a prolonged water deficit environment ( [[#Stan--2019|Stan and Sanchez-Azofeifa, 2019]] ). Tropical montane forests are highly sensitive to warming and associated changes in cloud cover and moisture, with evidence that such forests are already being impacted through ‘browning’ (loss of biomass) from increased warming since the 1990s (Krishnaswamy et al., 2014).

Besides higher temperatures, current climate risks also depend on regional responses to a variety of climate events. For example, tropical biomes across the three continents may respond differently to ENSO events in terms of carbon fluxes and balance. During the 2015–2016 ENSO event, different processes were dominant for the carbon fluxes anomaly in the tropical regions. In Asian forests, this anomaly was primarily derived from enhanced fire occurrence, in African forests through increased ecosystem respiration (from higher temperatures), and in South American forests by ecophysiological effects, through the gross primary production (GPP) expressed as reduced carbon uptake (Liu et al., 2017; van Schaik et al., 2018). It has also been shown that the probability of drought spells at the beginning and end of the rainy season is higher in the areas with the highest deforestation (Leite-Filho et al., 2019). Furthermore, it has been observed that Amazon rainforest resilience is being lost faster in regions with less rainfall and in parts of the rainforest that are closer to human activity ( [[#IPCC--2014|IPCC, 2014]] ; Seiler et al., 2015) (CCP7.3.6). Conversely, it has been pointed out, on the basis of vegetation indices, that temperature has a greater influence on resilience than does precipitation, and tropical forests are more resilient to climate change when they are more diverse (Feng et al., 2021) (CCP7.3.6).

Biomes such as seasonally dry tropical forests subject to higher variability in rainfall or other climatic factors may be more resilient to fire and drought (Pulla et al., 2015; Liu et al., 2017), though there could be changes in species distributions as a result of disturbances (Allen et al., 2017). A regime of long-term, high rainfall variability seems to be critical in determining the overall resilience of tropical forests and savannas to climate disturbances (Ciemer et al., 2019), highlighting the heterogeneity of the tropical landscape to climate risk. Similarly, forest composition, nutrient limitations and biodiversity can influence forest resilience to disturbances. Recent evidence suggests that the degree of forest disturbance also affects the mechanisms through which biodiversity influences forest functioning (Schmitt et al., 2020). Neotropical secondary forests also showed high resilience by maintaining their biomass through high productivity and rates of recovery following major disturbances (Poorter et al., 2016). However, the possibility of tropical forests reaching ‘tipping points’ in their resilience and experiencing rapid die-off cannot be ruled out (Verbesselt et al., 2016).

<div id="CCP7.3.5" class="h2-container"></div>

<span id="ccp7.3.5-projected-impacts-of-climate-change-on-tropical-forest"></span>