Explainer-Why are migrants crossing the U.S.-Mexico border in record numbers?

Asylum-seeking migrants try to cross a barbed wire that was placed by members of the Texas National Guard on the banks of the Rio Bravo river, the border between the United States and Mexico, with the purpose of reinforcing border security and inhibiting the crossing of migrants to United States, seen from Ciudad Juarez, Mexico January 7, 2023. REUTERS/Jose Luis Gonzalez

(Reuters) - U.S. President Joe Biden is visiting the U.S.-Mexico border for the first time since he took office in January 2021 on Sunday, ahead of a visit to Mexico and after announcing new measures to reduce border crossings.

What is happening at the U.S.-Mexico border now and why are there record numbers of crossings?