The narrow argument would be that, temporally speaking, savannas and colored fruits are rare even on Earth. For any solar-powered primary producer in any theoretical biosphere, there is a basic evolutionary height advantage- you increase the percentage of the time you are in sunlight, spread reproductive tissues over a wider area, and cast shade on nearby competitors. As soon as Earth plants developed vascular systems for vertical nutrient transport (~350 million years ago), forest-morphologies began to dominate the most fertile land areas, so that open areas correlated with geographically distant harsh conditions or a lack of nutrients (deserts, tundra, inland mountains).
The last 60 million years or so have been the exception to this rule, leading to the distinctive savanna ecosystems of the Cenozoic. They really took off after an evolutionary innovation in photosynthesis, C4 carbon fixation, which has its own environmental contingencies. The drought tolerance and efficiency in carbon fixation of these plants are responsible for the existence of ‘fertile’ areas that also have high visibility- and in particular, the close proximity of dense forests and open plains (and coastlines where there are coastlines). As such, the geographic feature is highly contingent on a specific evolutionary pathway within a particular atmospheric regime- and the window could have been closed after a brief period of time by further developments.
The broader argument would point out that, as the wiki page notes, C4 carbon fixation evolved independently a lot, implying that it is closely adjacent to many plant types. The ‘height race’ in terrestrial primary producers may even increase the probability of this development, since it exacerbates the problem of evapotranspiration. If our method of chemical photosynthesis is a common first step in the early development of many planetary biospheres, then C4 carbon fixation may be a common development as well. Whenever you set up primary producers with a certain capacity for internal structure, in cool and dry climates, C4 organisms may be an expected result. We might phrase this argument, ‘the dominance of forest-like ecologies is not stable in evolutionary timescales’.
The even broader argument is that these geographic requirements are not strictly related to savannas and jungles per se; the relevant contingency is ‘environment that selects for erect poses and color vision in a nutrient-rich area’. These factors are not in tension in any obvious way, so we’d need a clever reason to say that this is a great filter.
It’s hard to argue that anyone does, I suppose.
The narrow argument would be that, temporally speaking, savannas and colored fruits are rare even on Earth. For any solar-powered primary producer in any theoretical biosphere, there is a basic evolutionary height advantage- you increase the percentage of the time you are in sunlight, spread reproductive tissues over a wider area, and cast shade on nearby competitors. As soon as Earth plants developed vascular systems for vertical nutrient transport (~350 million years ago), forest-morphologies began to dominate the most fertile land areas, so that open areas correlated with geographically distant harsh conditions or a lack of nutrients (deserts, tundra, inland mountains).
The last 60 million years or so have been the exception to this rule, leading to the distinctive savanna ecosystems of the Cenozoic. They really took off after an evolutionary innovation in photosynthesis, C4 carbon fixation, which has its own environmental contingencies. The drought tolerance and efficiency in carbon fixation of these plants are responsible for the existence of ‘fertile’ areas that also have high visibility- and in particular, the close proximity of dense forests and open plains (and coastlines where there are coastlines). As such, the geographic feature is highly contingent on a specific evolutionary pathway within a particular atmospheric regime- and the window could have been closed after a brief period of time by further developments.
The broader argument would point out that, as the wiki page notes, C4 carbon fixation evolved independently a lot, implying that it is closely adjacent to many plant types. The ‘height race’ in terrestrial primary producers may even increase the probability of this development, since it exacerbates the problem of evapotranspiration. If our method of chemical photosynthesis is a common first step in the early development of many planetary biospheres, then C4 carbon fixation may be a common development as well. Whenever you set up primary producers with a certain capacity for internal structure, in cool and dry climates, C4 organisms may be an expected result. We might phrase this argument, ‘the dominance of forest-like ecologies is not stable in evolutionary timescales’.
The even broader argument is that these geographic requirements are not strictly related to savannas and jungles per se; the relevant contingency is ‘environment that selects for erect poses and color vision in a nutrient-rich area’. These factors are not in tension in any obvious way, so we’d need a clever reason to say that this is a great filter.