What would have been the fate of hydrogen peroxide if MnO2 was not added?

Hydrogen peroxide, H2O2, decomposes naturally at a very slow rate to form oxygen gas and water.
When manganese dioxide, MnO2, is added to a solution of hydrogen peroxide, the rate of the reaction increases significantly. Manganese dioxide acts as a catalyst for the decomposition of hydrogen peroxide, meaning that it is not consumed in the reaction.
If no MnO2 was added to the H2O2 the decomposition of the H2O2 would be very slow.