Even so, several case studies have linked climate change to increased violent conflicts between farmers and herders in Nigeria, Kenya and Sudan, but have found mixed results for Mali and Tanzania. Evidence is also ambiguous and highly contested for high-intensity conflicts such as civil wars. Claims have been put forward that climate change-related droughts, in combination with other factors, had facilitated the civil war in Darfur, the Arab Spring in Egypt, the Syrian civil war, the Islamist insurgency in Nigeria, and the Somali civil war. Yet some studies have suggested that there is very little evidence for several of these causal claims, including for the cases of Darfur, Egypt, Syria, and Ghana.