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IPCC Special Report on Climate Change and Land: Multi-Dimensional View

  Mar 18, 2020

IPCC Special Report on Climate Change and Land: Multi-Dimensional View

What are the special reports of IPCC?

Intergovernmental Panel on Climate Change (IPCC) published its special report on climate change and land recently.

The IPCC first published a special report on 1.5C of warming in 2018.The land report is the second special report from the IPCC.  Third – on oceans and the cryosphere – is due in September 2019.

The aim of these special reports is to provide “an assessment on a specific issue”. They complement the main “assessment reports” that the IPCC publishes every five or six years.

What is the importance of land for us?

The land provides the “food, feed, fibre, fuel and freshwater” without which human society and its economy “could not exist”, the report says. This provision is under threat from rising global temperatures and “unprecedented” rates of land and freshwater exploitation in recent decades.

Land plays an important role in the climate system

Land is already under growing human pressure and climate change is adding to these pressures. Agriculture, forestry and other types of land use account for 23% of human greenhouse gas emissions. At the same time natural land processes absorb carbon dioxide equivalent to almost a third of carbon dioxide emissions from fossil fuels and industry as we will see ahead.

When land is degraded, it becomes less productive, restricting what can be grown and reducing the soil’s ability to absorb carbon. This exacerbates climate change, while climate change in turn exacerbates land degradation in many different ways.

Can we reverse the climate change impact?

The choices we make about sustainable land management can help reduce and in some cases reverse these adverse impacts.

In a future with more intensive rainfall the risk of soil erosion on croplands increases, and sustainable land management is a way to protect communities from the detrimental impacts of this soil erosion and landslides. 

How are drylands, desertification and climate change connected?

Roughly 500 million people live in areas that experience desertification. Drylands and areas that experience desertification are also more vulnerable to climate change and extreme events including

1. Drought,

2. Heatwaves, and

3. Dust storms, with an increasing global population providing further pressure.

The report sets out options to tackle land degradation, and prevent or adapt to further climate change.

New knowledge shows an increase in risks from dryland

1. Water scarcity,

2. Fire damage,

3. Permafrost degradation and

4. Food system instability, even for global warming of around 1.5°C

Food security will be increasingly affected by future climate change through

1. Yield declines – especially in the tropics –

2. Increased prices,

3. Reduced nutrient quality, and

4. Supply chain disruptions.

The report records that about one third of food produced is lost or wasted. Reducing this loss and waste would reduce greenhouse gas emissions and improve food security.

Does climate change have a relation to dietary choices?

Some dietary choices require more land and water, and cause more emissions of heat-trapping gases than others. Balanced diets featuring plant-based foods, such as coarse grains, legumes, fruits and vegetables, and animal-sourced food produced sustainably in low greenhouse gas emission systems, present major opportunities for adaptation to and limiting climate change

How does global warming impact agriculture?

Global warming – along with associated changes in rainfall patterns – has

1.    Altered the start and end of growing seasons,

2.    Contributed to regional crop yield reductions,

3.    Reduced freshwater availability,

4.    Put biodiversity under further stress and

5.    Increased tree mortality

What is land degradation and how is climate change linked to it?

Land degradation means long-term reduction or loss of at least one of the following: biological productivity, ecological integrity, or value to humans.”

This definition encompasses temporary or permanent decline in quality of soil, vegetation, water resources or wildlife – or the deterioration of the economic productivity of the land, such as the ability to farm the land for commercial or subsistence purposes.

Why is land degradation taking place?

Major degradation processes and their connections with climate change include, for example the gradual breaking down and removal of rock and soil. This is through some force of nature, such as wind, rain and/or waves, but can be exacerbated by activities including ploughing, grazing or deforestation.

A loss of soil fertility is another form of degradation. This can be through a loss of nutrients, such as nitrogen, phosphorus and potassium, or a decline in the amount of organic matter in the soil.

Forest degradation and deforestation are other sources of land degradation.

Is land degradation linked to climate change?

1. Land degradation is linked to several climate variables, such as temperature,

2. Precipitation,

3. Wind, and

4. Seasonality.

Can you give a detailed account of the connection?

Climate change can affect the land through both gradual changes in temperature and rainfall patterns, as well as changes in the distribution and intensity of extreme events.

Coastal erosion as affected by sea level rise and increased storm frequency/intensity. In cyclone prone areas (such as Bay of Bengal) the combination of sea level rise and more intense cyclones will pose a serious risk to people and livelihoods

Warming conditions and changing rainfall patterns will also “trigger changes in land- and crop management, such as changes in planting and harvest dates, type of crops etc.

Establish the food security link

The report notes that “changes in extreme weather and climate have negative impacts on food security through regional reductions of crop yields”. For example, it says that on average over recent decades, around 10% of cereal production has been lost globally because of extreme weather events.

What is the rain link?

The air can generally hold around 7% more moisture for every 1C of temperature rise. This means a warmer climate has the potential for more intense rainfall events, which “increase the erosive power of rainfall and hence increase the likelihood of water erosion”, the report says.

For example, in central India, “there has been a threefold increase in widespread extreme rain events during 1950-2015, which has influenced several land degradation processes, not least soil erosion”.

One potentially lethal consequence of increased rainfall and the accompanying land degradation is an increase in landslides.

Heavy rainfall and flooding can also “delay planting, increase soil compaction, and cause crop losses”, the report says, and “flooding associated with tropical cyclones can lead to crop failure from both rainfall and storm surges”. In some cases, this flooding can affect yields more than drought, the report notes – particularly in tropical regions, such as India.

Can you explore the climate change- heat wave/stress link?

Heatwaves are projected to increase in frequency, intensity and duration in most parts of the world and drought frequency and intensity is projected to increase in some regions that are already drought prone. 

Extreme heat events can reduce photosynthesis in trees, restrict growth rates of leaves and reduce growth of the whole tree, the report notes. Forests can become less resilient to future heat stress as extreme events occur more often, the report adds, and “widespread regional tree mortality may be triggered directly by drought and heat stress (including warm winters) and exacerbated by insect outbreak and fire”. 

“Global warming will exacerbate heat stress thereby amplifying deficits in soil moisture”, the report says. This will “increase the rate of drying”, the report adds, “causing drought to set in quicker, become more intense and widespread, last longer and could result in an increased global aridity”.

Any positive outcome on agriculture? 

The report does, however, stress that some aspects of climate change can improve the condition of the land. One example is “CO2 fertilisation”, where higher levels of CO2 in the atmosphere bolsters plant growth. (The CO2 fertilization effect or carbon fertilization effect is the increased rate of photosynthesis in plants that results from increased levels of carbon dioxide in the atmosphere. The effect varies depending on the plant species, the temperature, and the availability of water and nutrients.)

Explain the land as a carbon sink and what happens when there is global warming.

The land stores around 40% of all the CO2 released by humans. Most of this carbon is held in forests, which absorb CO2 during photosynthesis and then use it to build new shoots, leaves and wood. Some carbon is transferred to forest soils when plants die. Thus land is an important carbon sink. When soils are dry, plants stop carrying out photosynthesis. Plants lose water when they perform photosynthesis. Therefore, many species stop when water supplies are depleted, meaning they aren’t taking in carbon anymore. The loss of water during photosynthesis is called “transpiration” and it has a cooling effect on the surrounding environment. As a result, when it is dry and transpiration stops, it can result in warming temperatures. Warming temperatures increase rates of respiration – the loss of carbon from soil and vegetation.