The online forms for work reports and trail assessments do not accept images larger than 500 kB.
Photoshop and other image processing software usually have a bulk processing function that allow you to resize all of your photos all at once. One such program that is available to download for free is FastStone Photo Resizer.
There are also websites that will reduce photo size online (though this is usually one photo at a time). One option is Pic Resize.
If you’ve taken the photos on your phone (for iPhones), you can also email them to yourself – when you send them, an option pops up asking you to select what size you would like to send them as.