You might check if there is a state or local incentive program to remove hazardous trees. As fas as federal taxes are concerned, there are no deductions or credits. Trees actually add to the property value in most cases, so removing them creates a loss in property value—but losses on personal property are never deductible.
If you can get an appraiser to agree with your argument about risk and tell you that your property has increased value because of the removal of the risk, then the cost of the removal would be added to the cost basis of your property, which might lower your taxable capital gains when you sell.
