短语讲解：
1. Development specialists say agricultural investments can be structured in ways that do not involve buying land – for instance, getting companies to collaborate with small-holder farmers.
collaborate with合作,与敌人合作,通敌
例句：The main aim now is to find a company to collaborate with.
现在的主要目标是找到一家公司合作。
2. But he says there is no evidence to back up these perceptions.
back up支持，证实；增援，后援
例句：He backed up his arguments with facts.
他以事实支持自己的论点。
3. According to Cotula, where outside investm
