What natural cause can lead to wildfires?

Spontaneous heating refers to a natural process where organic materials, such as compost, mulch, or fallen leaves, can generate heat through microbial decomposition. If the heat produced exceeds the material's ignition temperature, it can lead to combustion and ignite a wildfire. This phenomenon does not require any human intervention, making it a natural cause of wildfires.

The other options involve human activity or management practices. Forestry management generally aims to prevent wildfires through controlled burns and maintenance of forest health. Illegal dumping could introduce flammable materials but is still classified as a man-made cause. Flammable construction pertains to building materials and practices that could contribute to fire risk but are again entirely human-influenced. Thus, spontaneous heating stands out as the correct choice because it represents a natural occurrence that can initiate wildfires without any external causative factors.