Khat has one property that has shaped everything about it: the active compound cathinone degrades within a couple of days of picking, converting to a much weaker substance. The leaf must be consumed fresh.
For most of its history that confined khat to its growing regions and their immediate surroundings, and it is why khat, unlike coffee, never became a global commodity despite a comparable history and an easier preparation. Modern air freight changed this, and daily flights carrying khat from Ethiopia and Kenya to diaspora communities created an export trade of real economic weight, followed by bans in the United Kingdom, the Netherlands and elsewhere that removed it again.
The consequences at the growing end are substantial. Khat is far more profitable than coffee or food crops and it is harvested continuously rather than seasonally, so it has displaced both across large areas of Yemen and Ethiopia. In Yemen it consumes a very large share of scarce irrigation water in one of the most water-stressed countries in the world, which makes it a factor in food security rather than only a social question.
Its harms are contested and appear to be real but moderate: dependence, dental and oral problems, sleep disruption and cardiovascular effects, with psychiatric effects reported at heavy use. The atlas records the Sufi devotional use as its religious dimension, and notes that this is now a small part of a much larger and largely secular practice.