Field notes from Uganda 3: How do you solve a problem like savannah?

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Savannah in Queen Elizabeth National Park

We’ve just returned from a four-day trip to Queen Elizabeth National Park, one of Uganda’s flagship tourist destinations. It’s an extensive tract of savannah where one can readily see buffalo, elephants, hippos, and, if you’re lucky, lions or leopards.

What you won’t see are giraffes or zebra. Put aside for now that these glaring omissions are the result of staggering levels of poaching during the civil war. Their continued absence is a deliberate policy on the part of Uganda Wildlife Authority, who maintain the parks such that no single site contains the full complement of large animals. The rationale is that tourists will then travel around more and spread their largesse across the country. The obvious question is why would a wildlife tourist choose to come to Uganda when they could go on safari in Kenya or Tanzania and see all the big game in the same place?

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My curtains in QENP, which are the only place in the park to find giraffes and zebra.

Whatever one makes of this policy, it strikes at the heart of one of the most contentious debates in African conservation — how should savannahs be managed? Should it be to maximise the revenue from tourists, the enjoyment of local visitors, to minimise conflict with communities in and around the park, or to create systems as close to ‘natural’ as possible, whatever that is assumed to mean?

The problem is threefold. Firstly, there are a complex set of processes which act to create and maintain savannahs. While landscapes composed of scattered trees surrounded by grass form spontaneously in semi-arid areas with a pronounced dry season, there are large parts of the world where several types of vegetation are possible. They could turn into grasslands, savannahs, scrub or even closed-canopy dry forest. Multiple outcomes are possible.

Which one is found at any given site depends not solely on the climate but on the densities of large herbivores and the fire regime. Herds of species such as buffalo favour grasses, which are tolerant of grazing, and prevent woody seedlings from establishing. Larger animals like elephants feed on and break up woody vegetation. Grasses are also highly tolerant of fire, whereas tree seedlings are vulnerable, which means that regular fires hold back the trees and maintain open areas.

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Fires keep trees in check and promote grasses.

The twofold problem in the modern era is a dramatic reduction of the densities of large herbivores, and increased control of burning. This has led to shrub encroachment, widely believed to be a management problem. But this points towards the second issue, which is that there is no clear baseline to work towards.

Photographic records from a century ago show clearly that woody vegetation has expanded at the expense of open grasslands. Yet even when these photos were taken, they represented the state of savannah systems following several centuries of colonial game hunting and land management. This built on thousands of years of occupation by hunter-gatherers and native herdsmen, who were at the time being driven from the land. A general shortage of reliable palynological evidence (long-term pollen records) only further confounds the issue. We have no accurate means of determining what savannahs ‘should’ look like, or what that even means. Change is constant, from the scale of seasons to alterations in the balance between woody plants and grasses throughout the ice ages.

Savannahs are really a dynamic mosaic in which the shifting fortunes of trees and grasses are determined by changes in the climate, the populations of large animals, and the frequency of fire. The concept of ‘climax’ vegetation is of no use here. In a wet tropical rain forest it’s clear what state the system will default to once left alone. In a savannah we can only wait and see, or manage for what we prefer.

The final problem is that two other notable and crucial species are missing from these savannahs. The first is a tragic indictment of the greed and stupidity of humans — rhinos. The landscape in QENP is dominated by large¬†Euphorbia candelabrum, which are practically inedible to all the local species, but are greatly favoured by rhinos. How different would this park look if the rhinos returned? Right now it’s a rhino buffet. If only we could guarantee their safety, and an end to their pointless exploitation for the sake of a medical myth, the landscape would appear very different.

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These large Euphorbia are delicious for rhinos, but ignored by everything else (elephant for scale). Would they be so abundant if rhinos were still here to eat them?

The last species that’s missing is easily forgotten because no-one realises that they’re threatened. It’s a keystone species, crucial as an ecosystem engineer, seed disperser and top predator. It’s also a charismatic primate averaging 60 kg in size, with fascinating behaviour and cascading impacts across savannah ecosystems. Does this ring any bells?

Modern humans evolved in Africa around 150 000 years ago from an ancestor which was also a savannah ape. For thousands of years they have managed these landscapes, particularly through fire. Burning was a tool not only to drive out game but to maintain open areas where hunting was easier and grassy plains where prey were abundant. More recently domesticated cattle spread across Africa, and all this long before the depredations of the modern era. These days we tend to assert that the only way to protect natural systems is to exclude people. But what if people are part of the system? Would it be reasonable to reintroduce the rhino but not the hunter-gatherer?

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