Beyond 1.5°C: What Climate Overshoot Means for Southeast Asian Agriculture, Forests, and Natural Resources

Overshoot matters not only because 1.5°C is crossed, but because higher and more prolonged warming can increase the likelihood of cumulative impacts.

UNEP (2026b) distinguishes a long-term global warming level above 1.5°C, measured against the 1850–1900 preindustrial baseline, from a temporary exceedance in an individual year. Human-induced warming is nearing 1.4°C. Its optimistic scenario of full implementation of national climate plans and additional net-zero pledges puts peak warming at approximately 1.8°C; other scenarios suggest higher peaks. The October emissions gap assessment likewise emphasizes minimizing both the height and duration of overshoot (UNEP 2026a). These are conditional global pathways, not predictions for individual Southeast Asian countries.

For AFNR systems, prolonged exposure matters because impacts can compound. Repeated droughts and floods can weaken household assets and institutions; heat can affect crops, livestock, fisheries, aquaculture, forests, and workers; and ecosystem degradation can weaken water regulation, pollination, soil functions, and coastal protection (UNEP 2026b).

Regional evidence shows that exposure does not determine vulnerability on its own. Using a livelihood vulnerability index informed by the Intergovernmental Panel on Climate Change (IPCC) approach, Murniati et al. (2017) found greater overall vulnerability among non-organic than organic rice-farming households in a selected study area of Lampung Province, Indonesia. Individual indicators differed: organic households were more vulnerable in water security, while non-organic households were more vulnerable in agricultural profile and food security. The result should not be generalized to all organic and non-organic systems. Sajise et al. (2017) examined responses to coastal erosion, flooding, and saltwater intrusion in communities in Indonesia, the Philippines, and Vietnam. Adaptation patterns differed by hazard and location, while trust and gender-related differences in household labor availability also influenced responses. These findings underscore the importance of social conditions and institutions in adaptation.

These studies help explain why similar climate pressures can produce unequal effects. They do not establish how such differences will evolve under future overshoot.

Having adaptation options does not ensure resilience if farmers cannot access, use, and sustain them.

UNEP (2026b) identifies extreme heat as a serious hazard for crops, livestock, fisheries, aquaculture, and forestry. It also cites projections of a decline of up to 14 percent in global food production by 2050 in the absence of effective adaptation. This is a conditional global estimate, not a Southeast Asian forecast or a figure that can be applied uniformly to individual production systems.

Production outcomes depend on more than climate exposure. In the Philippines, Stuecker, Tigchelaar, and Kantar (2018) found that soil moisture variability, largely driven by the El Niño–Southern Oscillation, was associated with rice production variability during 1987–2016. Rainfed upland rice was more sensitive to soil moisture variation than irrigated paddy rice, with effects also differing by season and region. This illustrates why adaptation must reflect local water conditions and production systems.

Landicho et al. (2015), studying smallholders in the Molawin-Dampalit Sub-Watershed in the Philippines, documented farmer-reported climate changes and associated effects on crops, pests and diseases, yields, and income. Reported coping measures included replanting, changing crops, water management, earlier harvesting, and applying pesticides and fertilizers. Such responses demonstrate action under existing stress, not necessarily effective or environmentally sustainable adaptation under prolonged warming.

Adaptive capacity also depends on institutions and knowledge. Landicho et al. (2019) documented training, cross-farm visits, agroforestry demonstration plots, climate awareness activities, and links between scientific knowledge and policymaking in selected upland communities in Indonesia, Lao People’s Democratic Republic (Lao PDR), the Philippines, and Vietnam. The authors reported strengthened dimensions of adaptive capacity involving community assets, knowledge, innovation, institutions, and forward-looking decisions; the study did not test long-term resilience under overshoot.

Manalo et al. (2025) found that many adaptation mechanisms in Central Luzon, particularly technologies, were available but often poorly utilized, while efforts addressing the social dimension of adaptation were scarce or absent. Availability, therefore, should not be mistaken for effective deployment or sustained benefit. The authors recommend deployment plans for identified adaptation mechanisms and stronger efforts to help farmers use their entitlements.

Wassmann et al. (2022) describe climate-smart villages in Myanmar, Lao PDR, Cambodia, Vietnam, and the Philippines, with particular attention to rice seed systems. In a Lao PDR example, community-based seed systems were complemented by farmer field schools, participatory variety selection, seed fairs, and climate-risk mapping. The authors emphasize matching technologies and practices to local biophysical conditions and community needs.

Taken together, these studies suggest that adaptation requires more than a portfolio of technologies. Access, local suitability, institutional support, actual use, and performance over time all matter. A measure that helps households cope with present variability may require adjustment or replacement as climate stresses intensify (Landicho et al. 2015, 2019; Manalo et al. 2025; Wassmann et al. 2022).

Even if global temperatures later decline, damaged ecosystems may recover slowly, incompletely, or not at all.

UNEP (2026b) finds that some ecosystem impacts can persist long after peak warming. Species extinction is irreversible; changes in ecosystem composition and function may recover slowly or incompletely. These are different outcomes and should not be treated as equivalent.

This matters directly for agriculture and rural livelihoods because forests, wetlands, soils, pollinators, mangroves, and coastal ecosystems support water regulation, production, fisheries, soil fertility, and protection from storms and erosion. Damage to these functions may continue affecting communities even after global temperatures begin to decline. Shaw et al. (2022) also identify significant climate risks to Asian terrestrial and coastal ecosystems, fisheries, and aquaculture; this wider assessment provides regional context rather than a direct projection of post-overshoot recovery.

Overshoot also changes conservation planning. As climatic conditions shift, suitable ranges for species may move beyond existing protected-area boundaries. UNEP (2026b) therefore emphasizes ecological connectivity and anticipatory spatial planning. In Southeast Asia, these considerations are relevant to linked forests, watersheds, mangroves, and coastal habitats, although appropriate interventions depend on local ecological conditions.

Protection and restoration serve different purposes, and restoration approaches do not produce identical benefits. Natural forest restoration and plantation-based approaches can differ in biodiversity, water regulation, and carbon outcomes; afforestation in unsuitable ecosystems may increase water stress or harm native biodiversity (UNEP 2026b). Protecting functioning ecosystems may therefore avoid losses that later restoration cannot fully reverse.

For AFNR planning, restoration success should be judged through more than hectares planted. Relevant outcomes include survival and regeneration, ecosystem function, species diversity, water effects, carbon storage and permanence, ecological connectivity, and effects on surrounding communities. In forests and coastal ecosystems alike, monitoring should distinguish activities completed from ecological functions actually maintained or recovered.

Mitigation can limit the magnitude and duration of overshoot, but adaptation remains necessary. At the same time, land- and water-based climate interventions may generate competing demands on resources.

UNEP (2026b) emphasizes that mitigation and adaptation are needed throughout overshoot. Delayed mitigation increases the risk of future damage and can place greater pressure on resources needed for adaptation. The October 2026 emissions gap assessment reinforces that faster global emissions cuts are essential to limit peak warming (UNEP 2026a).

Global net-zero greenhouse gas emissions could produce a very gradual temperature decline after peak warming. A sufficiently rapid return toward 1.5°C would require deep and sustained emissions reductions alongside global net-negative carbon dioxide emissions, with human-caused carbon dioxide removals exceeding human-caused carbon dioxide emissions (UNEP 2026b). CDR must complement, not replace, rapid emissions reductions. UNEP (2026b) discusses afforestation, ecosystem restoration, bioenergy with carbon capture and storage, and direct air carbon capture and storage. Cutting methane and other short-lived climate pollutants can also reduce near-term warming, with methane mitigation in rice cultivation and livestock production relevant to AFNR systems.

Land-based CDR can create trade-offs. Afforestation may provide climate and adaptation benefits where ecologically appropriate, but large-scale or poorly located projects can compete with food production and water supplies or displace native biodiversity. Large-scale bioenergy raises related land-use concerns (UNEP 2026b). Carbon storage claims also require attention to durability and the possibility of future reversal.

In Southeast Asia, these decisions are particularly consequential where agricultural production, forests, biodiversity, water supply, carbon storage, and rural livelihoods depend on the same landscapes. A measure that increases carbon storage does not necessarily improve food or water security, and its effects may differ among land users.

Water creates a similar planning challenge. UNEP (2026b) notes that rainfall, flows, and availability may change unevenly during overshoot and any subsequent decline. Lower global temperatures would not necessarily restore earlier regional water conditions.

Household-level evidence also illustrates how resources constrain responses to water-related hazards. Almaden et al. (2019), studying rice-farming households affected by seawater intrusion in Northern Mindanao, found that adaptation varied according to farmers’ propensity to adapt, the variety and diversity of measures adopted, their feasibility, and the conditions of seawater intrusion. Their analysis identified farmers’ economic capacity as a major influence on adaptation. The findings illustrate how water-related hazards and household resources can constrain adaptation choices.

For Southeast Asian AFNR systems, land and water decisions should assess mitigation, adaptation, food production, biodiversity, tenure, and livelihoods together, including how benefits and costs are distributed. Project appraisal should therefore examine ecological suitability, water requirements, possible displacement, and safeguards for affected communities.

Adaptation measures need to remain adjustable because what works during early warming may not remain suitable near peak warming or during a later decline.

Agricultural practices developed for hotter conditions may need to change if risks intensify or later shift. Water infrastructure designed around one rainfall pattern may face different conditions; protected areas may no longer match the climatic ranges of the species they were established to conserve (UNEP 2026b). These are planning possibilities, not observed results of post-peak cooling in Southeast Asia.

Adaptation under overshoot must therefore be flexible, forward-looking, and iterative. This does not mean postponing action until future conditions are certain. It means acting now while retaining the ability to monitor performance, revise assumptions, and change course.

Regional studies illustrate elements of adaptive capacity relevant to this approach. Landicho et al. (2019) report improvements in community assets, knowledge and information, innovation, institutions, and forward-looking decision-making through capacity-development initiatives. Wassmann et al. (2022) demonstrate the relevance of combining locally appropriate rice seed systems with supporting climate-smart agricultural interventions. These studies provide useful lessons for adaptive planning, although they do not evaluate performance across a future overshoot pathway.

The additional challenge is identifying when measures are approaching their limits. For Southeast Asian AFNR systems, this may involve maintaining diverse seed and crop options, revising extension advice, designing adjustable water-management rules, preserving ecological connectivity, and avoiding restoration designs dependent on a single species or function. Monitoring should link observed changes in climate exposure and intervention performance to explicit review or decision points.

Long-lived investments, such as irrigation infrastructure and major land-use changes, warrant particular attention because they can constrain future choices. One proposed planning approach is to use adaptation pathways: assess plausible conditions, choose measures that work across scenarios, monitor locally appropriate indicators, set triggers for review, and adjust or transform the response when needed. A decision trigger is an observed condition or performance threshold that prompts reassessment, not a universal numeric standard. These are proposed planning steps; their effectiveness across overshoot stages requires further evaluation.