Thread by @valmasdel

THREAD

Key findings from the IPCC Special Report on Climate Change and Land were presented at #COP25 this week

unfccc-cop25.streamworld.de/webcast/joint-…

This series of tweets is my presentation, if you'd rather read than watch the video.

In this report, land refers to soil, vegetation and other living organisms, water, as well as our settlements and infrastructures.

Land provides the principal basis for our livelihoods and well-being including the supply of food, freshwater and multiple other ecosystem services, as well as biodiversity.

Land provides the basis for many other ecosystem functions and services that are essential for us.

For instance, the world's terrestrial ecosystem services have been valued on an annual basis to be approximately equivalent to the annual global Gross Domestic Product

Land is under growing human pressure with unprecedented rates of land and freshwater use

Human use directly affects more than 70% (likely 69-76%) of the global, ice free land surface.

Expansion of areas under agriculture and forestry and enhanced agriculture and forestry productivity have supported food availability for a growing population and changes in consumption.

The potential net primary production is the difference between the amount of carbon accumulated through photosynthesis and lost by plant respiration, in the absence of land use.

People currently use one quarter to one third of this land’s potential net primary production for food, feed, fibre, timber and energy.

These changes have contributed to loss of natural ecosystems (e.g. forests, savannahs, natural grasslands and wetlands) and declining biodiversity

About a quarter of the Earth’s ice-free land area is subject to human-induced degradation

Soil erosion from agricultural fields is estimated to be currently one or two orders of magnitude higher than the soil formation rate.

Data available since 1961 show that global population growth and changes in per capita consumption of food, feed, fibre, timber and energy have caused unprecedented rates of land and freshwater use.

Since 1961, the total number of ruminant livestock has increased by more than 50%.

Cereal yields have been multipled by 2.

The use of inorganic nitrogen fertilizer has been increased by nearly 9-fold. The use of irrigation water has roughly doubled.

Since the pre-industrial period (1850-1900) the observed mean land surface air temperature has risen considerably more than the global mean surface (land and ocean) temperature (GMST).

From 1850-1900 to 2006-2015 mean land surface air temperature has increased by 1.53°C (very likely range from 1.38°C to 1.68°C) while global mean surface temperature (land and ocean) increased by 0.87°C (likely range from 0.75°C to 0.99°C).

Warming has resulted in an increased frequency, intensity and duration of heat related events, including heat waves in most land regions.

The frequency and intensity of droughts has increased in some regions (including the Mediterranean, west Asia, many parts of South America, much of Africa, and north-eastern Asia) and there been an increase in the intensity of heavy precipitation events at a global scale

Global warming has led to shifts of climate zones in many world regions, including expansion of arid climate zones and contraction of polar climate zones.

As a consequence, many plant and animal species have experienced changes in their ranges, abundances, and shifts in their seasonal activities

Vegetation greening is observed by satellites over the last three decades in parts of Asia, Europe, South America, central North America, and southeast Australia.

Causes of greening include combinations of an extended growing season, nitrogen deposition, CO2 fertilisation, and land management.

Vegetation browning has been observed in some regions including northern Eurasia, parts of North America, Central Asia and the Congo Basin, largely as a result of water stress.

Globally, vegetation greening has occurred over a larger area than vegetation browning.

In some dryland areas, increased land surface air temperature and evapotranspiration and decreased precipitation amount, in interaction with climate variability and human activities, have contributed to desertification.

These areas include Sub-Saharan Africa, parts of East and Central Asia, and Australia.

Since 1961, the annual area of drylands in drought has increased, on average by slightly more than 1% per year, with large inter-annual variability.

About 500 million people lived within areas which experienced desertification between the 1980s and 2000s.

The highest numbers of people affected are in South and East Asia, the circum Sahara region including North Africa, and the Middle East including the Arabian peninsula.

The frequency & intensity of dust storms have increased over the last few decades due to land use and land cover changes + climate-related factors in many dryland areas resulting in increasing negative impacts on human health, in e.g. Arabian Peninsula, Middle East, Central Asia

Climate change exacerbates land degradation, particularly in low-lying coastal areas, river deltas, drylands and in permafrost areas due to changes in rainfall intensity, heat and water stress, permafrost thaw, coastal erosion and sea level rise.

The food system is under pressure due to population growth and changes in consumption patterns and is vulnerable to climate change

Data available since 1961 shows the per capita supply of vegetable oils and meat has more than doubled and the supply of food calories per capita has increased by about one third

Currently, 25-30% of total food produced is lost or wasted

An estimated 821 million people are still undernourished

Changes in consumption patterns have contributed to about 2 billion adults now being overweight or suffering from obesity

Climate change has already affected food security due to warming, changing precipitation patterns, and greater frequency of some extreme events.

In many lower-latitude regions, yields of some crops (e.g., maize and wheat) have declined, while in many higher-latitude regions, yields of some crops (e.g., maize, wheat and sugar beets) have increased over recent decades

Climate change has resulted in lower animal growth rates and productivity in pastoral systems in Africa

There is robust evidence that agricultural pests and diseases have already responded to climate change resulting in both increases and decreases of infestations

Based on indigenous and local knowledge, climate change is affecting food security in drylands, particularly those in Africa, and high mountain regions of Asia and South America

Land plays a key role in the global climate system. Changes in land conditions affect global and regional climate through sources and sinks of greenhouse gases, energy, water and aerosols between the land surface and atmosphere.

Agriculture, Forestry and Other Land Use (AFOLU) activities accounted for around 23% of total net anthropogenic emissions of GHGs or 12 +/- 3 GtCO2e per year during 2007-2016.

13% of CO2, 44% of methane (CH4), and 82% of nitrous oxide (N2O) emissions from human activities globally during 2007-2016

If emissions associated with pre- and post-production activities in the global food system are included, the emissions are estimated to be 21-37% of total net anthropogenic GHG emissions

Global models estimate net CO2 emissions of 5.2±2.6 GtCO2/yr from land use and land-use change during 2007-16 (13% of total CO2 emissions). They are mostly due to deforestation, partly offset by afforestation/reforestation. No clear trend in annual emissions since 1990.

This sector accounts for 44% of methane emissions in 2007-2016 . Ruminants and the expansion of rice cultivation are important contributors to the rising methane concentration.

The N2O emissions from this sector are rising, and represent 82% of total N2O emissions.

Anthropogenic N2O emissions from soils are primarily due to nitrogen application, including inefficiencies (over-application or poorly synchronised with crop demand timings).

There has been a major growth in emissions from managed pastures due to increased manure deposition. Livestock on managed pastures and rangelands accounted for more than one half of total anthropogenic N2O emissions from agriculture in 2014.

Emissions from agricultural production are projected to increase, driven by population and income growth and changes in consumption patterns

The natural response of land to human-induced environmental changes such as increasing atmospheric CO2 concentration, nitrogen deposition, and climate change, resulted in global net removals of 11.2 +/– 2.6 Gt CO2 yr–1 during 2007-2016, equivalent to 29% of total CO2 emissions.

The sum of the net removals due to this response and the AFOLU net emissions gives a total net land-atmosphere flux that removed 6.0+/-2.6 GtCO2 yr-1 during 2007-2016

Land is simultaneously a source and a sink of CO2 due to both anthropogenic and natural drivers, making it hard to separate anthropogenic from natural fluxes.

Global models and national greenhouse gas inventories use different methods to estimate anthropogenic CO2 emissions and removals for the land sector.

Both produce estimates that are in close agreement for land-use change involving forest (e.g., deforestation, afforestation), and differ for managed forest.

Global models consider as managed forest those lands that were subject to harvest whereas national inventories define managed forest more broadly.

On this larger area, inventories can also consider the natural response of land to human-induced environmental changes as anthropogenic, while the global model approach treats this response as part of the non-anthropogenic sink.

Consideration of differences in methods can enhance understanding of land sector net emission estimates and their applications.

Future net increases in CO2 emissions from vegetation and soils due to climate change are projected to counteract increased removals due to CO2 fertilisation and longer growing seasons

The balance between these processes is a key source of uncertainty for determining the future of the land carbon sink.

The potential of increasing soil organic carbon decreases as climate change intensifies, as soils have reduced capacity to act as sinks for carbon sequestration at higher temperatures.

Projected thawing of permafrost is expected to increase the loss of soil carbon. During the 21st century, vegetation growth in those areas may compensate in part for this loss.

Changes in land conditions, either from land-use or climate change, also affect regional climate.

Changing land conditins can reduce or accentuate warming and affect the intensity, frequency and direction of extreme events.

Drier soil conditions can increase the severity of heat waves, and vice versa wetter soil conditions can reduce it.

When forest cover increases in tropical regions, cooling results from enhanced evapotranspiration.

END.

For the other parts of the key findings related to projections, risks, adaptation and mitigation response options, enabling response options and action in the near term, please see the full video or go to the report page,
ipcc.ch/report/SRCCL