Despite the common "wisdom" that the federal government is universally bloated, there's little evidence to suggest the forest service has an excessive number of employees given the size of their job. For context they're less than half the size of Facebook, and my non-expert hot take is that managing all that federal land sounds like the more complicated and labor intensive job. If they were running pretty lean already, firing 10% of the workforce could potentially result in job functions with no one to do them, and that goes downhill pretty fast.
The firings were also exclusively focused on firing new employees, regardless of role or performance, simply because they were easy to fire. That makes the forest service (and every other federal agency) as unattractive employer, which will make it much harder to recruit new employees as people naturally retire or leave. That 10% reduction is going to snowball into a larger number over time, even if more people don't get fired, which I suspect they will.
Less important but worth noting is that while the stated goal is to "drain the DC deep state swamp" or whatever, what that apparently really translates into is firing forest service employees, who are spread out all over the country and not what most people think of when it comes to "the deep state". In the name of fighting the bureaucratic boogeyman, they're hurting people like this.