HorizontalEPI focuses on environmental co-ordination across policy sectors, whileverticalEPI is concerned with environmental co-ordination in one particular sector without cross-sectoral modes of interaction (Lafferty and Hovden2003: 12-14). Although vertical integration is in part instigated by horizontal requirements (Feindt2010), this paper will limit itself to vertical EPI within the agricultural sector.

Can someone help understand what the author is referring to?

Reference:

https://www.tandfonline.com/doi/full/10.1080/13501763.2017.1334085