Drought, conflict and high food prices will drive millions of people in West Africa's Sahel region into malnutrition and further insecurity without immediate aid, three United Nations agencies warned on Thursday.This could be one of the worst crop seasons in several years and many families may exhaust their food reserves early, according to the World Food Program, the UN children's agency and the Food and Agriculture Organisation. Poor rainfall in parts of Mali, Niger, Burkina Faso, Chad, Mauritania and Senegal has ruined livestock and harvests, leading to an early start of the hunger season.More than 1.6 million children are at risk of severe acute malnutrition this year, 50% more than in the Sahel's last major crisis in 2012, the agencies said at a press conference.Insecurity in the Sahel has forced tens of thousands of people to leave their homes and has led to the closure of schools and disruption of basic social services. Such vulnerabilities create an environment where extremism can thrive, the UN agencies said.Fighters affiliated with the Islamic State group and al-Qaeda already are active in the region."You do have a whole cohort of people with little access to education, little job opportunity, conflict, everyone at home, movement to (displacement) centres where they basically have very little to do. This is all creating a situation where there is fertile ground for groups that do not have noble intentions to recruit these people in their ranks," said Marie-Pierre Poirier, Unicef's regional director for West and Central Africa.Early action will prevent a downward spiral, the agencies said."If we don't do anything, what will they do? Die, join extremist groups, migrate? Migrate where?" asked Abdou Dieng, the WFP regional director for West and Central Africa. "We must invest in programs in the Sahel."The FAO called for $128m to prevent a deteriorating situation for 2.5 million pastoralists and agro-pastoralists. WFP asked for $284m to provide assistance to some 3.5 million people across the six countries. And Unicef seeks $264m to reach nearly 990 000 children at risk of severe malnutrition.* Sign up to News24's top Africa news in your inbox: SUBSCRIBE TO THE HELLO AFRICA NEWSLETTERFOLLOW News24 Africa on Twitter and Facebook.