Enter The Hothouse Age 

275 Million Years PE

It is now five million years since the end of the Mid-Ultimocene. The hothouse age has arrived.

Serina is now a global wetland, as a carbon dioxide-heavy atmosphere traps heat and moisture in a self-perpetuating cycle of nearly constant rain that floods the land and turns the world into a maze of ponds, rivers, lakes and inland oceans. Seas are at their highest ever levels with no ice caps remaining, and oceans have claimed the edges of all continents hundreds of miles inland, forming thousands of islands along coastlines around the globe.  A hothouse world lacking temperature changes throughout the year has virtually removed all trace of seasons except near the poles, where they are defined by changing day length from light to dark. Serina is now warm and wet all year, every year, and everywhere. It has never been warmer, ever, with a global air temperature now averaging a steamy 81 degrees Fahrenheit (27 Celsius). This temperature is not only an average of all global regions, but is very likely to be the temperature you will experience anywhere from pole to equator, for heat is distributed extremely evenly across Serina’s surface so that even in the polar winter the air near the ground remains balmy. 

This climate - hot but not dry - is highly favorable to life in general, as many organisms have now adapted to this new - and very different - condition. Trees have already returned to Serina, evolving from the ramblerooters, hiddenwoods, and other woody ice-age survivors quick to take advantage of the new endless summer, and have spread across Serinaustra and across offshore islands the world wide. Yet forests are almost nonexistent across the entire northern mainland: thorngrazers, still the most successful land animals by numbers, so heavily graze the landscape as to completely prevent the growth of trees wherever they can reach. Only the steepest slopes escape their appetites, as well as islands in deep water, for thorngrazers are heavy and dense, making them very unsuited swimmers. 

Plants and animal biodiversity has already recovered to pre-ice age levels, but this new world is not a paradise. Storms build readily in the hot atmosphere, and thunderstorms form everywhere nearly daily, burning fast and angry as they blow across the land and light the sky with electricity. Warm oceans likewise regularly produce immense, towering cyclones bigger than any in known Earth history, which may batter the coastal regions with winds in excess of 300 miles per hour. Inland, the muggy climate favors the proliferation of parasites and the spread of pathogens which in a colder world were of little concern, requiring animals to be incredibly resilient - or incredibly good at keeping themselves clean. This is a world of equal parts endless abundance and incredible danger. Food, for most, is everywhere - but so too can be death around any corner. To thrive here takes great caution, the sharpest wit, or the most brutal strength, and Serina’s animal life has found ways to utilize all three in the hothouse - a period already shaping up to be an age like no other. 

Notable Biomes and Regions of the Hothouse (At a Glance)

Soglands: a habitat made by and for thorngrazers through their intensive feeding, sogland is Serinarcta’s primary biome and can be broadly defined as a saturated, often flooded grassland with a high water table and nearly complete absence of trees. 

Longdark Swamp: a forested wetland that covers much of Serinaustra and is subject to seasonal extremes of day length, culminating in a months-long summer where the sun does not set under the horizon, and likewise alternating with a polar winter in which the world falls into shadow for an entire season in an eerie, glowing, nocturnal world. 

Polar Basin: the largest of Serina’s 7+ distinct inland seas, this immense freshwater lake was carved by glaciers and now sits at the top of Serinarcta over the north pole. It is subjected to the same seasonal changes as the longdark swamp, except at opposite times of year. Creatures and plants alike must cope with total darkness for almost half the year, but are rewarded for their struggles in the summer as the sea is covered with fast-growing floating vegetation that draws the attention of migratory aquatic animals from outside the basin.

Centralian Sea: a low-lying basin near Serinarcta's center, formed from a deep-burning, now flooded coal seam, this freshwater drainage contains the largest underwater openings into the coalseam cave system.

Coalseam Caves: a system of many often isolated caverns underneath parts of the central soglands formed by the burning of huge ancient coal seams, leaving hundreds of miles of hollow tunnels beneath the surface of the ground. Now mostly flooded, they are home to fascinating troglodyte organisms. Sinkholes into this realm are a hazard to large animals living above. 

Anstevan Archipelago: a flooded jungle island continent in the Serinaustran eco-region where sealumps, but neither foxtrotters or snowscroungers, are present.

Clearview Mountains: an upland vegetated hill region formed by end-ice-age volcanoes. This is where the reaper colony settled 5 million years before, when it was young and only supported grass. It now supports open forests.

Southern Saltswamp: a landscape of brackish and saltwater flooded forests.

Great Blue Saltlake:  a nearly-seawater salty inland sea which is located at the center of Serinaustra. It was formed by a surge of seawater inland at the end of the Mid-Ultimocene, not from freshwater drainage as in other inland seas.

Arctic Plateau and Upland Plain: similar to soglands, but drier, these higher-elevation grasslands are above the water table and not flooded. Formed from end-ice-age volcanic activity, it still rains here daily, but the water rarely pools in long-lasting ponds, instead draining away through the loose, volcanic soil substrate. Fellstar landed on the upland plain near the Centrallian Sea, and there was found by Eve.

Zarreland: a continental island connected to the mainland by a series of small islands which are often separated by tides. In a few million years, these short-lived bridges will wash away for good and isolate its inhabitants.

Trilliontree Islands: an archipelago of several hundred small islands off the shore of the northern continent. Isolated away from ravenous but land-lubbing thorngrazers, they are now the most forested region of Serinarcta.

Equinoctial Ocean: the former icebox seaway - now deep and dark except for a few raised seamounts.

Meridian Seamount: all that is left of the flooded Meridian Islands is now a shallow water underwater island of sea-grass meadows inhabited by endemic animals that may live nowhere else, surrounded by a desert of deep open water they cannot cross.

Trang Island: this offshore Serinarctan island flooded just a few thousand years after the ice age. A shallow water seaway hundreds of miles wide now isolates it from the mainland. It combines northern and southern faunal groups, which have evolved in unconventional ways in the absence of expected competitors.

Unbroken Ocean: Serina's open seas are deeper than ever now, and again contain abyssal zones beyond the reach of sunlight. With surface temperatures so warm, the deep sea is now the only place that still gets cold. Upwellings of nutrients near to the surface nourish plankton in significant numbers, but are limited to near coastlines, leaving most open oceans virtual deserts where life is sparsely distributed.