Climate change, food and disease vectors, at a glance

Fossil-fuel use, forest clearance and food production can add CO2 or methane and reduce carbon uptake. Their accumulation changes the balance between energy entering and leaving Earth.

• Fossil fuels transfer stored carbon into CO2.
• Deforestation can release carbon and reduce uptake.
• Ruminant digestion is a methane source.

Keep in mind: The greenhouse mechanism concerns absorption and re-emission of outgoing infrared radiation. Ozone depletion is a different atmospheric process.

Warming can melt land ice, expand sea water, intensify several weather extremes and disrupt fresh-water supplies. Thawing frozen organic matter can release gases that add further warming.

• Land-ice melt and thermal expansion raise sea level.
• Fresh-water stress includes quantity and quality.
• Thaw can release CO2 or methane and amplify warming.

Keep in mind: Positive describes amplification. Thaw, gas release and further warming reinforce one another; the term does not judge the effect as good.

Organisms may shift towards suitable conditions, but movement is limited by habitat and life-cycle needs. Heat, altered water conditions and rising seas can stress entire coastal ecosystems.

• Range shifts depend on suitable accessible habitat.
• Bleaching is loss of coral partners or pigments, not automatically immediate death.
• Seagrass and mangroves have specific light, salinity and water-depth limits.

Keep in mind: Suitable habitat may be inaccessible or absent, and species differ in dispersal and requirements. A range shift is a possible response, not a guarantee of persistence.

Mangroves take up and store carbon, while their vegetation and roots can reduce wave energy and retain sediment. These benefits depend on conserving a functioning ecosystem.

• Carbon is held in biomass and sediment.
• Waterlogged sediment can slow decomposition.
• Roots and trunks can reduce wave energy and trap sediment.

Keep in mind: Their buffering and carbon-storage benefits are substantial but limited by conditions, area and ecosystem health. They cannot guarantee complete protection or unlimited emissions compensation.

Compare emissions for the same useful energy output across construction, operation and end of life. Solar and nuclear usually have much lower life-cycle emissions than fossil electricity; bioethanol depends strongly on production and land use.

• Compare equal useful output and the same boundary.
• Solar and nuclear have low operating carbon emissions but non-zero life-cycle footprints.
• Bioethanol needs land-use and production accounting.

Keep in mind: The balance also depends on land-carbon changes and production emissions. Clearing a forest for a fuel crop can add a large carbon cost.

Food footprints depend on production processes and land use. Ruminant meat often has a larger footprint than plant protein sources, but fair comparisons need the same nutritional or mass unit and a stated boundary.

• Animal feed and maintenance add production stages.
• Ruminants add methane; forest conversion adds a carbon cost.
• The comparison unit and boundary must be stated.

Keep in mind: Transport is only one stage. Production, methane and land-use emissions can be larger, so distance alone cannot establish the total footprint.

Heat, drought, floods and storms can reduce plant and animal production and make supplies less reliable. Sustainable responses protect future productive capacity as well as the next harvest.

• Connect a specific stress to a biological mechanism.
• Yield, reliability and access can all change.
• A response must protect future soil, water and ecosystems.

Keep in mind: Both variables changed. Separate controlled treatments are needed to distinguish their effects and any interaction.

Within suitable limits, warming can increase insect metabolic and developmental rates. Beyond tolerance limits, survival falls; Aedes development also requires the right life-stage habitat.

• Aedes: egg, aquatic larva, aquatic pupa, flying adult.
• Metabolism and development can accelerate within suitable limits.
• Survival and water availability matter as well as speed.

Keep in mind: Benefits occur only within suitable conditions. Excessive heat, dehydration and loss of breeding water can reduce survival and reproduction.

Warming can make some cooler places or seasons more suitable for vectors and pathogen development. Transmission still requires the right mosquito, the pathogen and contact with susceptible hosts.

• Dengue: virus and Aedes vector.
• Malaria: Plasmodium parasite and Anopheles vector.
• Warming can extend suitability; other conditions determine transmission.

Keep in mind: Dengue virus is mainly transmitted by Aedes, while malaria parasites are transmitted by Anopheles. Warming can affect their transmission systems but does not create either pathogen.