The East Africa Food Crisis Appeal by 13 charities comprising the Disasters Emergency Committee (DEC) includes the Christian groups Christian Aid, Cafod, Tearfund and World Vision.
The appeal is hoping to bring aid to more than 16 million people in the region that is on the brink of starvation and in urgent need of food, water and medical treatment.
Funds raised by the DEC appeal will go to those affected in Somalia, Kenya, Ethiopia and South Sudan, with the Government pledging to match public donations up to £5 million.
The UN formally declared a famine in parts of South Sudan in February.
Save the Children says that up to 19.5 million people urgently need help. The charity says that the last time famine affected this part of Africa six years ago, a quarter of a million people died – 130,000 of them children.
As well as the famine in South Sudan, in Somalia, 50,000 children are already at risk of death, and across Kenya and Ethiopia, hundreds of thousands of children are dangerously malnourished.
So why is famine spreading across East Africa?
Conflict is the fundamental reason in South Sudan. For 42 of the past 60 years, since well before the creation of the state of South Sudan, there has been war in the south of the country.
South Sudan plunged into civil war between warring militias in 2013, leading to widespread hunger.
Most of the population earns its living through farming but war and a worsening drought situation has made it impossible for them to farm.
As crop production has fallen and livestock have died, inflation has soared causing massive price rises for basic foodstuffs.
And as the fighting has continued, vital food being brought in to support the South Sudanese people has been blocked, with aid workers being attacked.
Around 50 per cent of harvests have been destroyed in some areas. Unlike other areas of East Africa, severe drought is not the primary cause, but it has intensified the situation.
In October 2016, South Sudan's inflation rate reached 836 per cent, making it the highest in the world.
Linked to the other factor – climate change – droughts are occurring in East Africa increasingly often, with the region suffering from major droughts in 2011 and in 2009.
Because of the frequency of such droughts, people have precious little time to rebuild their lives and their livelihoods between each event.
Drought has been especially acute across Somalia, southern and south eastern Ethiopia, and northern Kenya.
In Somalia, there has been no rain for three years leading to drought. This is exacerbated by the ongoing internal conflict in the country.
In northern Kenya, the communities are primarily pastoralists – nomadic and semi nomadic herders who rely on cattle and livestock as a means of maintaining a sustainable way of life.
In Ethiopia, 5.6 million people in the southern and south eastern regions of Ethiopia have been affected by a new drought after failed autumn rains in 2016. This has resulted in a critical shortage of water and pasture, leading to a sharp deterioration in condition of livestock and livestock deaths in some places. For these communities, the loss or livestock means a loss of or decrease in milk production, which is often one of the only sources of protein for families.
These countries depend on the two rainy seasons and when they fail, the effects can be catastrophic as they lose cattle and valuable pastures.
Christian Aid and Cafod say that climate change is a key factor in the crisis. The major 2011 drought in the region was a result of the El Niño phenomenon: lower than normal temperatures in the Pacific Ocean had serious effects on weather conditions around the world.
El Niño is a Pacific Ocean warming occurring every two to seven years, and is said by Christian Aid to be the cause of this current drought.
In 2017, the hunger crisis has been caused by severe and extreme weather shifts, part of the El Niño effect which has caused drought. In countries like South Sudan this has been exacerbated by conflict and economic collapse.
In northern Kenya during 2016, the long rains (March-May) performed poorly and the short rains (October – December) failed.
In Ethiopia, back-to-back seasons of poor or non-existent rainfall in 2015, exacerbated by the strongest El Niño weather pattern on record in the same year, led to the worst drought in decades in northern Ethiopia.