Quick Answer
If Earth's axial tilt became zero while its orbit stayed similar, the Sun would remain over the equator and most locations would experience much less seasonal change. The equator would receive broadly consistent sunlight through the year, while polar regions would have persistent low Sun angles. The planet would not have one uniform temperature: latitude, oceans, atmosphere and circulation would still control climate.
Earth's seasons are primarily a consequence of its roughly 23.4-degree axial tilt, not changes in the planet's distance from the Sun. As Earth orbits, each hemisphere alternately tilts toward and away from the Sun, changing sunlight angle and day length.
The simplest no-season scenario
Imagine Earth's axis becoming perpendicular to its orbital plane. The Sun would remain directly over the equator at the equinox-like position throughout the year. Day and night would stay much closer to twelve hours at most latitudes, and the dramatic migration of the subsolar point between the tropics would disappear.
The poles would be very different
At the poles, the Sun would sit very low on the horizon rather than climbing high during a polar summer. The absence of months-long polar daylight would profoundly change sea ice, snow accumulation and high-latitude ecosystems. Exactly how the climate would settle would depend on atmospheric and oceanic circulation.
Agriculture
Agriculture would not simply become easier because the weather was stable. Many crops are adapted to seasonal temperature and daylight cues, while others require cold periods or particular day lengths. Farmers could adapt crop choices and planting systems, but regional climates would still determine what grows well.
Established scienceSeasonality is not only about temperature. Plants can respond to photoperiod — the length of day — as well as temperature, rainfall and other environmental signals.
Would climate become identical everywhere?
No. Latitude would still matter because sunlight strikes different parts of a spherical planet at different angles. Oceans would continue moving heat, mountains would alter circulation, and the atmosphere would redistribute energy. Removing axial tilt removes one major seasonal driver, not the entire climate system.
Animals and migration
Many migrations are timed by seasonal changes in food, temperature and daylight. Removing those cycles would disrupt existing timing systems. Some species could adapt, while others could lose the environmental cues that currently synchronize breeding, migration or dormancy.
Axial tilt
Main cause of seasons
Near the equator
No-tilt subsolar latitude
Much more stable
Day length
Still present by latitude
Climate variation
The bottom line
A seasonless Earth would not be a permanently spring-like paradise. It would be a planet with a different distribution of sunlight, different polar conditions and a climate system that ecosystems and agriculture would have to relearn.