We need principals from all stakeholder groups in Davos to summon the imagination and commitment necessary to tackle the problem.

【翻译】我们需要达沃斯论坛所有利益相关团体的负责人，调动和给出解决问题所需要的想象力和承诺。

necessary to tackle the problem：这是一个形容词后带有不定式的“形容词短语”，作定语。修饰前文 the imagination and commitment， 相当于一个定语从句：the imagination and commitment which are necessary to tackle the problem

又如：

He had the ruthless streak necessary to carry him into the Cabinet.  

他具有进入内阁所必需的冷酷性格。

来自柯林斯例句