Why is in situ conservation needed alongside ex situ conservation?

In order to conserve ecosystems efficiently in the long term, the intra-specific diversity must be protected. Species will be able to respond to environmental changes (e.g. longer droughts due to climate change) through genetic adaptation only if there is sufficient diversity. The conservation of the entire intra-specific diversity ex situ is not feasible as it would be too resource-intensive. Therefore, the focus lies on in situ conservation. The "genetic reserve conservation technique" combines ex situ conservation with the complementary in situ conservation: on the one hand, a static pattern of intra-specific diversity is safeguarded in the gene bank; on the other hand, in situ conservation allows for the continuous adaptation of reproductive populations to changing habitat conditions. In situ conservation is thus, in contrast to ex situ conservation, dynamically oriented.