Complex sentence: The reed beds are grazed by Konik horses and Highland cattle while they are drained; this helps maintain the boundary between reed beds and open water areas and helps control reed density, providing open water feeding pools for bitterns within the reed beds.
Split into simpler sentences: The reed beds are grazed by Konik horses and Highland cattle while they are drained; this helps maintain the boundary between reed beds and open water areas. This control of reed density provides open water feeding pools for bitterns within the reed beds.