If an alternate Earth had an axial tilt of 45 degrees, what would the seasons look like? Being the most extreme tilt a planet can have before simply replacing North/South with East/West, obviously such a world would have rather extreme seasons, what just how extreme? What would these extreme seasons look like? What would their effect be on the ecosystem?
I'd imagine the 4 seasons area would have harsher degrees of winter, and get a glimpse of tropical summer.
On details that would make the dry land parts of earth are already smaller than we would naturally have (without global warming), cause the earth's pole area that didn't catch direct sunlight throughout the year are smaller.
At the ecosystem level, there may be a smaller pure tropical climate (or maybe there isn;t any at all), and most creatures are experiencing highly fluctuating seasons change. If this happens naturally from the very beginning, I expect a thick furry creatures like polar bear may developed a shedding cycle as part of their survival process in the summer, while others who don't developed a habit to survive.
Winter would be colder and summer would be hotter.
Overall there would be a greater gradient of temperature from the southern hemisphere to the northern hemisphere. That would result in stronger wind and sea currents.
How that would affect the environment and ecosystems is difficult to tell because there are many feedback effects involved. I would naively say that there would be way more hurricanes and tornadoes, thus making life more difficult in general.
Another effect would be that the Earth's magnetic field might deflect less solar radiation because it would be too inclined. There might be a higher level of radiation on the surface of such a planet.
However the odds of a 45 degree axial tilt planet are very small. Because planets are formed by accretion of dust around a massive sun, most debris are in the same accretion disk. Planets are tilted because in the late stage of accretion, a planet in formation is hit by another smaller planet (usually moon sized) at a certain angle, tilting the planet. However because most rocks are in the same accretion disk, for a planet to tilt to 45 degrees, you would need a planet of similar size to hit it from a large angle to cause such a tilt. Statistically the odds are small. That s why you don t see many planets with such a tilt in the universe.