Climate Change and Mosquito Breeding Grounds: Data, Mechanisms and Projections

1. Introduction

Mosquito-borne diseases remain among the largest infectious burdens on Earth. The World Health Organization estimated 282 million malaria cases and 610,000 deaths in 2024, roughly 9 million more cases than the year before, with the African Region carrying about 94% of cases (WHO, World Malaria Report 2025). Dengue is now the fastest-growing arboviral disease: 6.5 million cases were reported to WHO in 2023, then a record 14.1 million cases and 9,508 deaths in 2024, a twelve-fold rise over a decade (Haider et al. 2024, 2025).

Reported cases undercount reality; modelling studies put annual dengue infections on the order of 400 million, most of them mild or unrecorded (Bhatt et al. 2013). Chikungunya, Zika, West Nile virus, Japanese encephalitis and lymphatic filariasis add to the toll.

None of these numbers can be blamed on climate alone. Immunity, travel, urbanisation, drug and insecticide resistance, conflict, and funding all play large roles. But climate acts on the one thing every one of these diseases has in common: a small aquatic insect that must find standing water, warm enough and wet enough, to complete its life cycle.

This article asks a specific question: how does a warmer, wetter-in-places, drier-in-others, and more erratic climate change where, when and how intensely mosquitoes breed? We start with the biology, move through the climate drivers and regional geography, then look at real cities, and only then turn to data tables and projections.

2. Climate Change and Mosquito Populations: The Biology Behind the Problem

2.1 A life cycle split between water and air

Every mosquito passes through four stages in their life cycle: egg, larva, pupa, adult. The first three are aquatic; only the adult flies. Females need a blood meal to develop eggs, and this creates the gonotrophic cycle: feed, digest and mature eggs, lay eggs, repeat. Only females bite.

The larva (four growth stages, called instars) feeds on microorganisms and organic particles in the water. The pupa does not feed; over one to a few days, depending on temperature, it transforms into the adult, which emerges at the water surface. The practical consequence is that the size of a mosquito population depends on how much suitable water exists, how warm it is, and how long it lasts. Climate changes all three.

2.2 The main vectors and where they breed

Three genera do most of the damage, and they do not breed in the same places.

• Aedes aegypti and Aedes albopictus (dengue, chikungunya, Zika, yellow fever) are container breeders. They lay eggs just above the waterline on the walls of small containers (water storage jars, buckets, tyres, flowerpot saucers, roof gutters, air-conditioner trays). Eggs can survive drying for months and hatch when water rises to cover them. Both bite mainly by day and live close to people. Ae. aegypti is the more domestic, more heat-tolerant species. Ae. albopictus uses natural containers such as tree holes and cut bamboo as well as artificial ones, and temperate populations produce diapausing eggs (a dormant, cold-hardy state triggered by shortening days) that let it survive winters.
• Anopheles (malaria) females lay eggs singly on the water surface. An. gambiae and relatives generally favour clean, sunlit, shallow, often temporary pools: puddles, hoof prints, edges of streams, brick pits. An. stephensi, the main urban malaria vector in South Asia, is different: it breeds in overhead tanks, wells, cisterns and construction-site water. It has been detected in Djibouti (2012), Ethiopia and Sudan (2016), Somalia (2019), Nigeria (by 2020) and Kenya (2022), and modelling identifies African cities as at risk from it (Sinka et al. 2020).
• Culex quinquefasciatus and Culex pipiens (West Nile virus, lymphatic filariasis) lay egg rafts and prefer water rich in organic matter: blocked drains, septic systems, latrines, polluted ponds. (Japanese encephalitis is mainly carried by another Culex species, Cx. tritaeniorhynchus, which breeds in flooded rice fields.)

2.3 Why temperature controls everything: ectotherms and the extrinsic incubation period

Mosquitoes are ectotherms: their body temperature follows the environment, so nearly every rate in their lives is temperature-dependent: how fast eggs and larvae develop, how long adults live, how often females bite, and how quickly a pathogen matures inside them.

That last process is the extrinsic incubation period (EIP): the time from when a mosquito ingests an infected blood meal to when it can transmit the pathogen. For dengue virus, a meta-analysis estimated a mean EIP of about 15 days at 25 °C but only 6.5 days at 30 °C (Chan & Johansson 2012).

This matters because an adult female mosquito in the wild often lives only a couple of weeks. A pathogen that needs 15 days can only be passed on by the unusually long-lived; one that needs 6.5 days can be passed on by most. A five-degree change can therefore change transmission far more than it changes mosquito numbers.

(i) Rising mean temperature and warmer nights. Greenhouse warming is not uniform: night-time minima have risen faster than daytime maxima in many regions. Warmer nights matter because cold nights, not hot afternoons, limit mosquitoes in cool regions.

Effect: increase in cool zones, mixed near the optimum, possible decrease above about 34 °C.
Confidence: high for the physiological response, medium for local outcomes.

(ii) Changing rainfall: heavier downpours, longer dry spells, shifting monsoons. A warmer atmosphere holds more water vapour, so when it rains it tends to rain harder, and dry spells can lengthen between events. Heavy rain fills containers, drains and puddles; very heavy rain can also flush larvae away, so the immediate effect can be a short-term dip followed by a rebound as pools stabilise. Shifts in monsoon onset and withdrawal change when breeding starts and stops.

Effect: usually an increase, with strong regional differences and timing lags.

(iii) Flooding and stagnant post-flood pools. Floods create vast temporary habitat in low-lying land, and receding waters leave isolated pools that suit Culex and Anopheles. Post-flood surges in vector-borne disease have been reported in several regions, though attributing any single outbreak to a single flood is difficult.

(iv) Drought and its paradox. Less rain does not mean fewer mosquitoes. Where piped supply fails, households store water in drums, tanks and buckets, which is prime Aedes habitat. The 2014–15 water crisis in São Paulo, when many households stored water, was followed by a very large dengue season, and water storage is a plausible contributor, although it is hard to isolate from other factors. In rural Africa, shrinking rivers break into isolated pools in riverbeds that can suit Anopheles.

Effect: mixed and setting-dependent.

(v) Humidity and vapour pressure. Where warming outpaces moisture, the air can get drier at the same time as hotter, reducing adult survival; where moisture rises with temperature, survival is helped.

Effect: mixed.

(vi) Sea-level rise and salinity. Rising seas and storm surge push brackish water into coastal pools and aquifers. Salt-tolerant species such as Aedes taeniorhynchus and Ae. sollicitans (salt marshes of the Americas), Ae. detritus (Europe), and the malaria vectors An. sundaicus (brackish coastal Asia) and An. melas/An. merus (African coasts) may gain habitat, while freshwater breeders lose some. Even Ae. aegypti larvae have been found developing in brackish water in coastal Sri Lanka (Ramasamy et al. 2011).

Effect: mixed, with species turnover.

(vii) ENSO and other oscillations. El Niño and La Niña shift rainfall and temperature across whole regions. Links to dengue incidence have been documented in Thailand, Mexico and Puerto Rico (Johansson et al. 2009), and the 1997–98 El Niño floods in East Africa preceded a large Rift Valley fever epidemic (Linthicum et al. 1999). Climate change may alter ENSO behaviour, but that projection remains uncertain.

(viii) Altitude and latitude. Because air cools by about 6.5 °C per kilometre of altitude, one degree of warming raises the “same temperature” line by about 150 m. Malaria incidence in highland Ethiopia and Colombia has been shown to shift upward in warmer years (Siraj et al. 2014), although the causes of highland trends are debated, since land use, drug resistance and health services also change. At high latitudes, Ae. albopictus has spread northwards in Europe; one 2025 analysis estimated the northern edge of its establishment advancing at roughly 60 km per year (Lancet Planetary Health, 2025).

(ix) Shorter winters and longer seasons. Milder winters raise overwintering survival and start the breeding season earlier, extending the annual window in which transmission is possible.

4. Geography and Weather: Six Climate Regimes

The same climate signal produces different outcomes depending on the starting point.

1) Equatorial and humid tropical (Amazon, Congo basin, Indonesia, Malaysia). Warm and wet all year, so mosquitoes breed all year. The story here is intensification, not expansion: more intense rainfall peaks, hotter urban cores near the thermal ceiling, and rapid urbanisation.

2) Monsoon tropical and subtropical (South Asia, Southeast Asia, the West African Sahel fringe). Breeding is tightly tied to rainfall onset. Cases typically lag rain by weeks, because pools must form, larvae must develop, adults must feed and the pathogen must complete its EIP. Shifts in monsoon timing and intensity, plus longer warm seasons, are the key climate levers. Some studies project dengue transmission seasons in tropical lowland areas of Southeast Asia, sub-Saharan Africa and the Indian subcontinent lengthening by up to four months under the highest-emission scenario (Colón-González et al. 2021).

3) Semi-arid and arid (Sahel, Thar fringe, Horn of Africa). Breeding depends on episodic rain and on human water storage. A single heavy rain year can trigger epidemics in a population with little immunity. Very high temperatures reduce adult survival, so the projected effect of warming here is mixed.

4) Highland and montane (Kenyan and Ethiopian highlands, Andean valleys, Himalayan foothills). The temperature-limited frontier. Cool nights slow larval development and lengthen the EIP so much that transmission fails. Warming pushes these thresholds upward. One modelling study estimated that, under the highest emissions, tropical areas above 1,000 m in places such as Ethiopia, Angola, South Africa and Madagascar could gain up to 1.6 additional suitable months for malaria by 2070–2099 (Colón-González et al. 2021). Populations there often have little immunity, so outbreaks can be severe.

5) Temperate and Mediterranean (southern Europe, the US Mid-Atlantic and Southeast, temperate East Asia, southern Australia). Newly suitable zones for Ae. albopictus. Even where vectors are established, transmission windows in temperate climates are short: models suggest at most about three months per year (Mordecai et al. 2017).

Warming lengthens these windows, and introductions via used-tyre trade, transport and travel supply the virus. Europe has moved from isolated events to recurrent local transmission: in October 2024, Italy recorded the largest dengue outbreak in Europe, with more than 200 confirmed local cases, and 2025 brought an unprecedented number of locally acquired chikungunya outbreaks (Lancet Planetary Health, 2025).

6) Coastal and deltaic (Bangladesh, Mekong, Nile delta, US Gulf Coast). Flooding, storm surge and salinity intrusion interact with dense populations. Effects are mixed by species, but the flooding-and-displacement pathway usually raises risk.

A note on microclimate. Climate models work on grids many kilometres wide. A mosquito lives in a stairwell, a rooftop tank or a shaded drain. Water in a small dark container can be cooler by day and warmer by night than air temperature, and indoor conditions differ again. Regional averages therefore locate risk but do not resolve it.

5. City-Level Case Studies

Cities concentrate people and concentrate breeding sites. The examples below use real places and real published patterns; the “climate pressure” and “lever” lines are the author’s synthesis.

5.1 Urban mechanisms that cut across every city

• Urban heat island (UHI). Dense built-up areas retain heat and cool slowly at night. Warmer nights speed larval development and shorten the EIP. The effect is mixed in very hot cities, where midday surface heat can also exceed mosquito tolerance.
• Impervious surfaces and blocked drains. Concrete sheds rain quickly into drains; if drains are clogged with waste, they hold water instead of removing it.
• Discarded containers and tyres. Small, shaded, rain-catching, nutrient-rich: ideal Aedes habitat.
• Air-conditioner drip trays, plant saucers, roof gutters. Warm, sheltered and constantly refilled.
• Construction sites. Excavations, foundations and stored materials hold water for weeks.
• Rooftop tanks and unmanaged storage. Uncovered tanks, cisterns and drums, common where supply is intermittent.
• Poor waste collection and informal settlements. Water storage in drums, weak drainage and limited screening raise both breeding and exposure.
• Cooler and drier cores. Urban centres can also be drier than surroundings (little vegetation, fast runoff) and, in some cities, cooler by day than irrigated peri-urban land, so risk can be lower in the core and higher at the margins. Vegetation can help or hurt: a 2026 preprint from Montpellier reported higher Ae. albopictus survival in vegetated urban spaces, a caution for greening schemes that ignore water and shade management.

5.2 Mumbai, India

Regime: tropical monsoon, with the large majority of annual rain falling between June and September.

Vectors: Ae. aegypti (dengue, chikungunya), Culex (filariasis, nuisance) and urban An. stephensi (malaria).

Breeding sites: rooftop and ground-level water tanks, under-ground septic tanks, construction pits, discarded containers and tyres, blocked drains, clogged gutters and nullahs, AC outdoor units, and low-lying informal settlements where water is stored in drums. Tidal flooding and extreme rainfall can leave standing water across large areas.

Climate pressure: intense monsoon bursts, longer warm periods around the monsoon shoulders, and intensifying extremes such as the July 2005 deluge.

Lever: enforceable, routine source reduction on construction sites and tanks, combined with drainage maintenance timed before the monsoon; the lag between rain and vector peaks (roughly 2–6 weeks in many monsoon settings) makes pre-monsoon action valuable.