Complex sentence: The SSSI is economically important to the area because of the the tourists it attracts for birdwatching and other outdoor activities, and the combination of sensitive wildlife sites and large numbers of visitors means that management is necessary to protect vulnerable sites.
Split into simpler sentences: The SSSI is economically important to the area because of the the tourists it attracts for birdwatching and other outdoor activities. The combination of sensitive wildlife sites and large numbers of visitors means that management is necessary to protect vulnerable sites.