How would such a fork effect our network? Do we then need to pick a fork or does it happen automatically?

Uno implemented merge mining with Bitcoin at block 600,000 in May, 2015. Merge mining allows a Bitcoin miners to also mine for Uno. As a result the security of Uno's blockchain increased significantly. Bitcoin miners earn more for their hash, while contributing to the security of Uno's blockchain. Miners will continue to receive Uno block rewards for the next 300 years.