Impacts of Climate Change

By the time climate change becomes intolerable, it will take decades to reverse the impact.

Around us we see evidence of human impact on climate, with serious implications for environmental, economic and social sustainability. Core climate trends are:

• increased severity and frequency of weather events
• extreme precipitation events with flooding that will tax wastewater and sanitation systems
• increased evaporation and more intense and prolonged droughts, increased incidence of heat stress
• increasing forest fire risks
• earlier springs, warmer summers, leading to shifts in peak flow of rivers
• higher stream flows as glaciers melt, followed by decreased flow as glaciers disappear
• degraded water due to algal blooms and thermal pollution
• increasing pest outbreaks

Pattern shifts such as floods in low-lying communities and prolonged heat waves are already occurring. Global warming is leading to intense droughts between 10 and 30 degrees of latitude.

Natural systems are highly complex and interwoven. They are not stable, static phenomenon. They are constantly shifting, evolving and being interrupted by disturbances such as fire, pests, predators and human activity.

Plants and animals function within ecosystems and within a range of climatic conditions. Water availability, ambient temperature and the balance of nutrients all dictate the success of a species. If conditions change dramatically, plants and animals respond in several ways:

• timing of events such as blooming of flowers, opening of leaves, hatching of insects, shift to earlier in the spring
• migrations shift to earlier in spring and later in fall
• populations might shift to a new location, tree lines shift to higher elevations and higher latitudes
• bird species can be particularly affected by warming, shifting northward
• amphibians are affected by ultraviolet light, explosions of fungi and pathogens
• more species become extinct

Climate change strains ecosystems. Habitat degradation, pollution, overfishing and hunting also strain ecosystems. It is estimated that 1 million species are currently threatened with extinction. Once a species is extinct, all the diversity that it represents is lost. Species that are pushed to extinction will not return. Lives lost cannot be reclaimed.

Climate change has a cascading impact. Global warming leads to melting glaciers, thermal expansion of water and increased severity of hurricanes, which lead to rising sea level and regular occurrences of wildfires and floods—which lead to erosion damage; damage to buildings along coastlines; altered distribution of ecosystems; shifts in the range and morphology of species; changes in the timing of life cycle events and the rise in the number of endangered species.

Ecosystems change through the natural process of succession. The shift from tundra to shrubs and forests alters the energy budget and makes different demands on the hydrological cycle. Some species are expanding their range, while others are not doing well. Negative impact is more common.

Conservation for humans has now broadened to include the preservation of species that are not directly related to our own enjoyment and profit. Designating species as threatened or endangered is one tool for trying to delay or prevent extinction—preservation of habitat is another. Choosing which species to preserve is complicated.

Vulnerability

Vulnerability to climate change is determined by a number of factors including:

• the amount of temperature change: rising temperatures increase the likelihood of heat-related mortality
• the magnitude, distribution, character and rate of climate change
• the importance of systems and species. Are the systems affected keystone systems? Are the species affected keystone species?
• persistence of species, resilience, the ability of a system to return to a healthy state or adapt, following a change or shock
• the effect of pests on vulnerable and weakened species

Systems most likely to suffer the effect of climate change are sensitive to warming, changes in precipitation and extreme events.

Wetlands are among the most vulnerable ecosystems on earth. They are a natural barrier to flooding, they purify water, they are some of the most biologically rich habitats.

The fertilizing effect of CO₂ causes an increase in net primary production of vegetation.

Oceans

Oceans may have been taking up more than 90% of excess heat, a service which can’t continue. Corals are some of the first creatures to suffer from warming. Bleaching happens when temperatures rise about 1°. Carbon dioxide adds carbonic acid to the oceans and leads to acidification, damaging coral and other calcifying organisms.

Ocean currents are changing, disrupting circulation of warm and cold currents of water. Currents act as conveyor belts, moving heat (the Gulf Stream) and cold water. Some fish are migrating from 6 days to 6 weeks earlier, having an impact on the fishing industry and the web of interactions with other species.

Melting of land-based glaciers in the Antarctic and Greenland ice sheets will eventually cause a sea level rise of between 5 and 7 meters (35 feet). Thermal expansion which occurs when heated water expands is predicted to cause between 14-35 centimeters in sea level rise by 2100. Sea level rise floods small islands and coastal plains and affects the intertidal zones, mangroves and marshes.

Impact of Climate Change on People

The effect of climate change has direct impact on populations:

• extreme precipitation, heavy rainfall the rise in the sea level and storm surges lead to flooding
• hurricanes and cyclones damage buildings
• heat waves kill people and crops
• 150 million people live in cities with persistent water shortages

Food production, calorie intake, is in for a shock. Food production is reduced by:

• drop in stream flows, and the diminished availability of water
• heat, drought and storms cause crop destruction
• increasing cost of seed, labour and fertilizer, and intensive farming methods diminished soil quality and nutrient levels

The western diet puts strain on Earth’s freshwater resources.

Loss of healthy forests affects livelihoods

Poverty and global inequality are affected by climate change which is leading to:

• mass migrations
• breakdown of government effectiveness and social order (for example failed states – extreme examples being Haiti and Somalia)
• the spread of diseases
• negative effects on mental health