Contrary to popular belief, human ashes can actually be harmful to the environment if not properly treated because they have properties that make them potentially harmful to soil and plant life such as high pH levels typically around 12, high salt content, nutrient imbalance, and can alter soil composition and structure. Here is more explanation:

1. High pH levels: Human ashes typically have a pH of around 12 out of 14, which is extremely alkaline – the same as bleach or oven cleaner. This pH is around one million times for most plants to have healthy growth and can disrupt soil chemistry and harm seedlings growth.

2. High salt content: Cremated remains contain a high level of sodium, approximately the worth of one cup. This high level salt can inhibit photosynthesis and damage plant tissues.

3. Nutrient imbalance: While rich in calcium and phosphates, the levels of these and other minerals in human ashes are not balanced in a way that supports healthy plant growth.

4. Soil disruption: Scattering large quantities of ashes in one area can alter soil composition and structure.

Studies have shown that untreated human ashes can have severe negative impacts on plant life. One Melbourne study found that 90% of seedlings died within 21 days when planted in soil containing untreated cremated remains.