It(a system of conservation)tends to ignore, and thus eventually to eliminate, many elements in the land community that lack commercial value, but that are essential to its healthy functioning.

【翻译】它 (一种保护制度) 往往忽视，因而最终摈弃陆地生态群的许多因素，这些因素虽然缺乏商业价值，但对其健康运作至关重要。

【分析】

It (a system of conservation)（主语）tends to ignore, and thus eventually to eliminate, （谓语动词，tends 后是两个并列的不定式：to ignore 和to eliminate） many elements in the land community  （宾语） that lack commercial value, but that are essential to its healthy functioning.（两个并列的定语从句，分别用that 引导，修饰elements ）

【翻译技巧】由于定语从句较长（本身含有but 连接的两个转折意义的并列句），所以按照非限制性定语从句处理，单独翻译成一句。